根据语篇内容，用恰当的短语填空，使之意思完整。

     Thanks for your invitation. I’m sorry I can’t visit you this week. I am (1)_________________. This

evening I’m going to my cousin’s house. It’s my cousin’s birthday. Today I have a toothache, so I have to

see the dentist tomorrow. On Friday, there will be a math test, and I (2)_________________. On Friday

evening, a new film will be on, and I'm (3)_________________ with my friends.

总的趋势是剂量偏小是（）

A．根据儿童年龄计算

B．根据儿童体重计算

C．根据儿童体表面积计算

D．按成人剂量折算表计算

E．以上均不是