用户终端盒内ONU与光纤端子跳纤一般选用（）CM的短尾纤。
A.40
B.50
C.100
D.60
参考答案：B
—Look, it ____ again.
—Yeah. This is the third snow we ____ this spring.
A．will snow; are having
B．has snowed; had had
C．is snowing; have had
D．snows; have had
在食管癌的放射治疗中，脊髓照射剂量应控制在（）cGy以下
A.2500
B.3000
C.3500
D.4500
E.5000
