蜜蜂在空中飞行时要不断扇动翅膀才不会落下．从力的角度分析，不断扇动翅膀是因为 ．
力的作用是相互的
翻译以下短语并完成句子。
1. prefer sth. _____
2. prefer to do sth. ______
3. prefer doing
4. prefer A to B_____
5. prefer doing A to doing B_____
6. prefer sb. to do sth. _____
7. prefer to do... rather than do_____
8. Even on a cold day he prefers _____ out to play football _____ at home.
即使在寒冷的天气里他宁愿出去踢足球也不愿呆在家里。
垄断性竞争条件下企业的行为特征有？
