如图所示，分别用甲、乙两套装置将同一物体匀速提升相同的高度，所用的拉力分别为F_甲、F_乙，它们的机械效率分别为η_甲、η_乙，则F_甲____ F_乙，η_甲 ____η_乙（选填“大于”“小于”或“等于”）（不计绳重与摩擦，且动滑轮重小于物重）

下列相关叙述正确的有
①一对夫妇生了四个孩子，其中只有一个孩子患有白化病，则该夫妇一定均为杂合子。
②表现型相同的个体，基因型不一定相同。
③1个具有2对同源染色体的精原细胞通过减数分裂最终形成4种精子（不考虑交叉互换）。
④隐性基因是指在生物体不能表现的基因。

⑴I'm listening to music ____           A. but the teacher comes.

⑵Lucy is playing with her dog,____    B. but my friends come to play with me.

⑶The pupils are talking very loudly,____     C. but her mother calls her.

⑷A bus is coming,____                 D. but it starts to rain.

⑸We are having a picnic,____       E. but there are too many people on the bus.

The bear is tall. The dog is short.