【题目】During this period，many experts warned of mass starvation in the developing world populations were expanding faster than crop production.

【题目】No one knows caused the accident.

【题目】We really appreciate our learning environment, _________ we can have direct communication.

【题目】If you keep word, you will do what you promise before .

【题目】 the other astronauts accept his idea remains a question.

【题目】We must do as much as we to make our country better and more beautiful.

【题目】With only a small number of pandas left in the world，China is trying to clone the animal and save the endangered species.

【题目】Any violent acts that do harm to the world peace and mankind should be seriously .

【题目】These photos remind me the good old days we spent together.