Заполните пробелы соответствующими грамматическими формами.
Fill in the blanks with the proper grammatical forms.
1. The experiments … by him.
A. has been done C. have been done
B. were been done D. have done
2. The scientists … a wide variety of subjects.
A. were studied C. has studied
B. have studied D. are studied
3. The cell structure of the plants … by the scientists.
A. has been examined C. have examined
B. has examined D. had examined
4. … they already solved the problem?
A. Are B. Have C. Do D. Is
5. … he made observations?
A. Have B. Is C. Does D. Has
6. This theory has … a part of scientific knowledge.
A. become B. became C. becomes D. been become
7. Scientific knowledge has … greatly.
A. grow B. grown C. grew D. grows
8. All branches of science … closely interconnected.
A. have B. has C. are D. had
9. The tools and machines … our life and work easier.
A. makes C. have made
B. have been made D. are made
10. Since ancient times people … tools and machines.
A. have invented C. are invented
B. invented D. invents