a÷b×$\frac{1}{b}$÷c×$\frac{1}{c}$÷d×$\frac{1}{d}$等于（　　）

阅读下面短文，从短文后各小题所给的A、B、C三个选项中，选出可以填入空白处的最佳选项。

                                                          The New Baby

 The picture shows a family visiting their new baby in hospital. I think it's probably the evening, because the light is 1, so the father must have brought his children 2work.

 There are two children beside the baby, a boy and a girl. The 3 is a little older than his sister. He's about six or seven. He     4 proud. The girl looks very 5 to have a new sister.

 The father has his arm around6children. He looks proud as well. The mother is sitting 7. She looks happy 8a little tired.

 The baby is in the middle. I guess it’s a girl,9she is wearing pink clothes. The baby is10 despite (尽管，不管) all the noise and excitement.

下列与激素作用无关的实例是