根据我国膳食特点，我国各地区矿物质中严重摄入不足的是（） A.钙 B.铁 C.锌 D

休克性肺炎的临床表现，以下描述不正确的是（）

A.血压下降、脉压减小

B.面色苍白、烦躁不安

C.四肢厥冷、出冷汗

D.尿量增多

E.不发热或仅有低热

仔细观察大多数植物叶片的正面绿色较深而背面绿色较浅，主要原因是___________________________。

按要求完成下列各句。

1. He did some work this morning. (改成否定句)

    He __________ do __________ work this morning.

2. The boy next to Li Lei is my friend. (对划线部分提问)

     __________ __________ is your friend?

3. The playground is wet this morning. It must rain last night. (改为反意疑问句)

    The playground is wet this morning. It must rain last night. __________ __________?

4. "Are you going to visit Zi Gong next Week?" Father asked me. (改为间接引语)

    Father asked me __________ I __________ going to visit Zi Gong next week.

高致病性禽流感的特点主要是什么？

形成铸件表面粘砂的原因是（）。

A.熔铸温度过低

B.熔铸时间过长

C.包埋材料的耐火度高

D.铸件间间隔距离过近

E.包埋材料的化学纯度高