四、语法填空。
What will people look like in the future? Someone makes 13. prediction. In the future, people 14. (have) larger heads and bigger eyes. Larger heads will be able 15. (keep) larger brains. People will become much 16. (smart).
Why will people have bigger eyes? That's 17. people may go and live on other planets. They may be farther 18. the sun than the earth is. Then people need bigger eyes to see 19. (careful) and more clearly in the darker environment. Because UV radiations（紫外线）are stronger on other planets than those on the earth, 20. (people) skin（皮肤）won't be so white as it was before.
What's more, people will not need to open 21. (they) mouths to speak. They will talk by chips（芯片）in their heads.
However, someone 22. (not want) an appearance like this. Don't worry. People will look like this in at least 20,000 years.

13. a
14. will have
15. to keep
16. smarter
17. because
18. from
19. more carefully
20. people's
21. their
22. doesn't want

13. 考查固定搭配make a prediction，意为“做一个预测”，prediction是可数名词单数，此处表泛指，填a。
14. 考查一般将来时，句中"In the future"（在将来）是本单元核心的一般将来时标志，结构为will+动词原形，填will have。
15. 考查固定搭配be able to do sth.，意为“能够做某事”，填to keep。
16. 考查形容词比较级，副词much可修饰形容词比较级表程度加深，smart的比较级为smarter，意为“更聪明的”。
17. 考查表语从句连接词，前文用Why提问原因，此处用固定结构That's because...（那是因为……）解释原因，填because。
18. 考查固定搭配far from，意为“远离”，此处为比较级形式farther from，填from。
19. 考查副词的比较级，此处修饰动词see，且和后面的more clearly构成并列结构，需要将形容词careful变为副词carefully的比较级more carefully，符合“看得更仔细、更清楚”的语境。
20. 考查名词所有格，此处修饰名词skin，表达“人们的皮肤”，用people的所有格形式people's。
21. 考查形容词性物主代词，此处修饰名词mouths，需要将人称代词主格they变为形容词性物主代词their，意为“他们的”。
22. 考查一般现在时的否定形式，主语someone是不定代词，视作单数，谓语动词的否定需要借助助动词doesn't，后接动词原形want，填doesn't want。