细胞的大小形态：细胞很小，直径一般只有    ____     到      ____   ，要用    ____     才能看到。细胞的种类很多，形态千姿百态，如精子呈    ____    状、卵细胞呈____ 形、平滑肌细胞呈 ____     形、红细胞呈    ____    形、洋葱表皮细胞呈    ____     形等。

如图是模拟膈肌的运动示意图，请据图完成下列问题：

判断对错．

两个质数相乘的积一定是合数．

阅读下列短文，从文后各题所给的四个选项中选出一个最佳答案。

     Hearing is very important to all of us. We can 1beautiful music, nice songs of birds, the laughter of people or other different kinds of  2 in the world with our ears. 3 we must try to protect our ears. The following will tell you  4 protect ears.

    Listening to 5 usic a lot can be bad forears, especially when headphones are used. So 6 the volume(音) when you're wearing headphones or try not to wear headphones. You should give your ears a rest if you like wearing headphones.

    Before swimming, remember 7 earplugs （耳塞) into your ears or wear a swim hat to stop water from getting into your ears.

If you are going to a concert, wear earplugs to protect your ears 8 the terrible music! In fact, special earplugs can be made for you if you go to concerts a lot or if you are a musician yourself.

    See a doctor if your ears 9. Take some medicine if the doctor asks you to do so. Follow the advice above now and you won't be saying"what?"when you are getting 10.