为什么新生儿瞳孔相对较小（）

A.交感神经支配相对迟滞

B.对E-W核过量的核上输入

C.光诱导的瞳孔缩小反射敏感性增加

D.瞳孔开大肌未成熟

E.角膜相对较大

No sooner had he finished his talk______he was surrounded by the workers.

A. as
B. then
C. than
D. when