21. Donating money for charity is a __ thing for everyone to do to help the community. A. meant B. meaningful C. meaningless D. mean 22. Personal __ devices are useful for learning. C. electronic D. electronical A. electric B. electrical 23. These children have the __ to imitate animals' voice. C. disable D. disability A. able B. ability 24. Human activity is leading to the extinction of species and habitats and __ of bio-diversity D. lost B. losing C. loss A. lose 25. The animals are lovely and friendly, but sadly, they are __ Few of them exist in the wild D. endanger A. dangerous B. danger C. endangered 26. We have to __ the natural resources of our country. A. conservation B. conserve C. conserved D. conservational 27. He's stopped __ plastic bottles since he found out it causes serious damage to the environment. D. having bought A. to buy B. buying C. to have bought 28. David tried his best __ , but his girlfriend refused __ A. explaining; to listen B. explaining; listening C. to explain; to listen D. to explain; listening 29. Joe, let me __ you to plant the flowers! I'm free now. C. helping D. helped A. help B. to help

21. "Donating money for charity is a meaningful thing for everyone to do to help the community." Từ "meaningful" có nghĩa là có ý nghĩa, phù hợp với ngữ cảnh câu.<br />22. "Personal electronic devices are useful for learning." Từ "electronic" có nghĩa là điện tử, phù hợp với ngữ cảnh câu.<br />23. "These children have the ability to imitate animals' voice." Từ "ability" có nghĩa là khả năng, phù hợp với ngữ cảnh câu.<br />24. "Human activity is leading to the extinction of species and habitats and loss of bio-diversity." Từ "loss" có nghĩa là sự mất mát, phù hợp với ngữ cảnh câu.<br />25. "The animals are lovely and friendly, but sadly, they are endangered. Few of them exist in the wild." Từ "endangered" có nghĩa là có nguy cơ tuyệt chủng, phù hợp với ngữ cảnh câu.<br />26. "We have to conserve the natural resources of our country." Từ "conserve" có nghĩa là bảo tồn, phù hợp với ngữ cảnh câu.<br />27. "He's stopped buying plastic bottles since he found out it causes serious damage to the environment." Từ "buying" có nghĩa là mua, phù hợp với ngữ cảnh câu.<br />28. "David tried his best explaining, but his girlfriend refused to listen." Cụm từ "tried his best explaining" và "refused to listen" phù hợp với ngữ cảnh câu.<br />29. "Joe, let me help you to plant the flowers! I'm free now." Từ "help" có nghĩa là giúp đỡ, phù hợp với ngữ cảnh câu.