开始控制性降压3分钟时出现缺氧性脑电图改变，可能性最大的是()

A．脑血管强烈痉挛，引起脑缺血

B．降压过快，脑血管未及时调节

C．脑氧摄取不变，但供氧减少

D．血液被稀释，载氧能力减少

E．脑血管栓塞

句型转换。

1. Lucy has two rubbers in her pencil-box.(对划线部分提问)

_______ ________ rubbers does Lucy have in her pencil-box?

2. Lily does her homework in the evening.(改为否定句)

Lily ______ ______ her homework in the evening.

3. There are some birds in the tree.(改为疑问句)

________ there _________ birds in the tree?

4. Amy's friends have many presents for her.(改为同义句)

Amy's friends have ______ ______ presents for her.