1a   无脊椎骨                  2

1b   有脊椎骨                  3

2a   身体分节，有外骨骼        R

2b   身体不分节                S

3a   卵生，提问不恒定          4

3b   胎生，体温恒定            P

4a   生活在水中，用腮呼吸          Q

4b   生活在陆地，用肺呼吸     M

完形填空

　The  1  is getting colder, and soon winter  2  shorter. We live in warm houses and we  3  thick coats when we go outside. But 4  do animals stay warm in winter?

Adapt(适应)

    Some animals keep  5  in winter, so they must adapt to the changing weather.  6  warm, they may grow new, thicker fur in  7 autumn.

Migrate(迁徙)

    Some of the animals migrate. That means they travel to other places  8  the weather is warm or they can find food.

Hibernate(冬眠)

    Some animals hibernate for part or  9  of the winter. These animals usually find a cave or a hole under the ground to spend their winter. The body temperature of the animals drops, their heart beats more slowly and they breathe  10  .

如图，在▱ABCD中，E、F、G、H分别为AB、BC、CD、AD的中点，AF与EH交于点M，FG与CH交于点N．

（1）求证：四边形MFNH为平行四边形；

（2）求证：△AMH≌△CNF．