Questions 16 to 20 are based on the following passage.
Being a female tree is hard. A study of a species that can change sex has revealed that most striped maple trees die while female.
“We had a suspicion they were changing sex, which is relatively rare among plants" says Jenifer Blake-Mahmud at Princeton University. Between 2014 and 2017, she and Lena Struwe at Rutgers University in New Jersey observed the life cycles of 457 striped maples in New Jersey, recording their health, diameter and whether they had female or male flowers each spring.
They found that 54 per cent of the trees changed sex during that time, and one fourth of those did so at least twice. A model based on these findings showed that, contrary to previous suggestions, healthy trees were more likely to be male and a tree's size doesn't influence its sex.
The growth rate of trees that remained female for many years declined. Of the trees that died, 75 per cent had recently produced femtate flowers. “It's remarkable," says Blake-Mahmud.“When I see a tree thats dead and Iook back in my data sheet, it was almost always female the year before.'
It isn't clear why this is the case. It could be that female trees need more nutrients because they produce seeds, and it may increase the death rate of female trees, she says.
But it could also be that dying tres become female as a last effort to create offspring and pass their genes on to the next generation.
"These populations have a lot more male trees than female trees in general, so just by luck, a female has a better chance of being a parent of the next generation than a male," say Blake-Mahmud.“If you're going to die anyway, then being female is the way to go. That would make more evolutionary sense."
16. Which factor mentioned in the passage does NOT influence the striped maple trees' sex?
A. Health. B. Size. C. Season. D. Age.
17. The word“declined" (Line 1, Para. 4) is closest in meaningto.
A. got worse
B. died away
C. went down
D. wore out
18. Female maple trees need more nutrients because.
A. they create offspring
B. they change their sex
C. they are less healthy
D. there are fewer female trees
19. What can be inferred from the last paragraph?
A. Healthy maple trees are more likely to be female.
B. Dying maple trees are more likely to be male.
C. Female maple trees are less likely to be parents.
D. Sex changing could be the natural life process of the maple trees.
20. What's the best title of the passage?
A. Female Maple Likely to Die
B. A Contrast of Female and Male Maple Treesy
C. Relationships between Female and MaleMapleTrees(
D. Differences between Female and Male Maple Trees
PartII Vocabulary and Structure (共40小题，每小题1分，共40分)
Directions: There are 40 incomplete sentences in this part. For each sentence there are 4 choices marked A, B, C and D. Choose the ONE that best completes the sentence. Then you' re your answer by blackehing the corresponding ltter on the Answer Sheet.
21. Students were required to do while staying at home because of the COVID-19 pandemic.
A. much on-line homework
B. many on-line homework
C. a few on-line homework
D. few on-line homework
22. I was told to take two pills. __eight hours.
A. other B. every C. othersD. the other
23. It is accepted that children need friends of their age.
A. to play
B. to be played with
C. to be played
D. to play with
24. Mary is an able and responsible woman. That's why she was asked to
A. have over
B. take over
C. turm over
D. come over
25. Before classes, some teachers would ask their students to hand in their mobile phones to prevent them from
A. being distracted
B. being attracted
26. The audience were__because Mr Smith's presentation was.
A. confused; confusing
B. confusing; confused
C. confused; more confused
D. confusing; more confusing
27.- _What do you think of the popular actor?
-I've never seen a man withsense of humor
A. the better
B. the best
D. a better
28. Jackson a book about China Iastyear; but I have not read it yet.
A. has written
D. would write
29. It that Chinese economy has done well in shifting from high-speed development to quality growth.
A. has been widely agreed
B. has been widely agreeing
C. agreed widely
D. agrees widely
30. We were wondering whether you_____ come and have lunch with us on Sunday.
A. could B. should C. shall D. had better
31. IfI had started out earlier, I the fight to Beijing.
B. would catch
C. had caught
D. would have caught
32. He made another wonderful discovery,___ is of great importance to science.
A. which B. where C. in which D. that
33. Whether he could finish his task depends on how well prepared
A. he is
B. is he
C. can he
D. he can
34. I don't think. easy for students to master a foreign language within two years.
A. that B. it C. which D. what
35. No one is permitted to enter the museum without_his/herID card.
A. having to show
B. being shown
D. having shown
36. The fire fighters made all their efforts.the big fire.
A. to put out
B. to have put out
C. having put out
D. being put out
37.____ late frequently will do harm to yourhealth.
A. Stay up
B. Staying up
C. To have stayed
D. Having stayed
38. Only when you have obtained sufficient data.come to a sound conclusion.
A. you can
B. canyou C. do you
D. would you
39. Yesterday I went to see her,.that she had goneabroad a week before.
C. only to find
D. tohave found
40. Mary was the only one of the girls who,. praised in ourclass last week.