He didn't come __________ he was ill.

1. A.
   because
2. B.
   because of
3. C.
   as
4. D.
   since

He didn't come __________ he was ill.　　　

[　　]

A．because　　　　　　　B．because of

C．as　　　　　　　　   D．since

He didn't come to school yesterday, ____ he was ill.

A. if

B. because

C. when

D. before

He didn't come to school yesterday 　　　　 he was ill.　

[　　]

A．because　　　B．after　　　C．when　　　D．if