Giúp em bài này với ạ!em cảm ơn

Choose the word or phrase that best completes each sentence below. 11. The mother cat and A. his B. its 12. Scientists are looking for an A. effective 13. Millions of people. A. have visited 14. What A. happen 15. Once non-renewable energy sources are used_ A. out B. for C. up 16. Mary ...