特异性免疫在抗感染中有何作用?

在单元测试过程中，可将单元从概念上划分为私有单元和公开单元。以下哪个是私有单元的特征

A．固定的

B．完整的

C．正式的

D．变化的

非选择性抑制环氧酶的药物是（）。

A.阿司匹林

B.布桂嗪

C.塞来昔布

D.秋水仙碱

E.丙吡胺

（）四星级电冰箱冷箱冷冻室的温度与食品储藏期分别为。

A、低于－28℃、8个月

B、低于－24℃、6个月

C、低于－18℃、3个月

D、低于－15℃、2个月

企业购置固定资产、无形资产也属于投资。

Directions:

You just spent your summer holidays in Tom’s hometown, Tom’s home is at a small and quiet countryside. Now, you are going to write him a letter of thanks for all he and his family did for you during your stay there.

Imagine some details of the summary holidays. Write your letter in no less than 100 words. Write it nearly on ANSWER SHEET 2.

Do not sign your own name at the end of the letter; use "Li Ming" instead.

Do not write the address, (10 points)