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