She really impressed me a lot for I had never heard ______voice.

A．the more beautiful

B．a most beautiful

C． a much beautiful

D．a more beautiful

胎龄32周的早产儿，出生体重1600g，生后5h出现进行性呼吸困难。入院时呼吸不规则，经皮氧饱和度为75%。

为初步诊断，应首先进行的检查是（）

A.血气分析

B.胸部X线片

C.血常规

D.心脏超声

E.查卵磷脂/鞘磷脂（L/S）