如果父母双方的基因组成都是Aa，他们所产生的生殖细胞就有两种，一种是含有基因____ 的，另一种是含有基因____ 的。受精卵的基因组成就有三种可能____ 、____ 、____ 。

19世纪70年代巴黎公社失败的社会根源是

    Do you know George? He is a little monkey. He lives in a deep forest. He likes jumping and climbing trees. He is happy every day. But he has a shortcoming（缺点）. He is curious（好奇的）.

    One day an old man went by the forest. He cared a lot of hats. George saw the old man, and the old man saw George, too. The old man said to himself, what a lovely monkey! I will catch him. I will take him home.

    The old man sat down and thought over. George saw and also sat down. The old man had an idea. He put a hat on his head, and put other has on the ground, Then be pretended(假装)to sleep.

    George was curious and looked at the hats. "I will be nice if I put a hat on my head, "George thought. Then be climbed down from the tree, picked up a hat and put it on. The hat was too big, and covered George's eyes. George couldn't see. And the old man got up at once and caught him quickly.

Poor George!

下列四组多边形中，能密铺地面的是（　  ）
①正六边形与正三角形；②正十二边形与正三角形；③正八边形与正方形；④正三角形与正方形。