主动脉瓣第二心音增强可见于下列哪种疾病
A．主动脉硬化
B．心包积液
C．肺气肿
D．主动脉关闭不全
E．主动脉狭窄
参考答案：A
The split between humans and apes is believed by scientists______15 to 20 million years ago.
A．to be occurring
B．having occurred
C．to have occurred
D．to occur
市场中出售的食盐都添加了碘，如果人体中缺少了碘易得（ ）
A．软骨病
B．大脖子病
C．贫血
D．夜盲症
