孕期摄入过量有可能会导致胎儿畸形的营养素是()
A.铜
B.叶酸
C.维生素A
D.维生素B
E.维生素D
参考答案:C
------ Kate and Lucy are twins.
------ Oh, I ______ why they looked so alike.
A.wonder
B.have wondered
C.was wondering
D.had wondered
可控硅触发电路不该触发时,其触发回路电压应小于()
A.0.15~0.25V
B.0.3~0.4V
C.0.35~0.45V
D.0.5~1.0V