John was seen ____ in by the back door, but nobody saw him ___.
A.to come…to leave
B.come… leave
C.to come… leave
D.come…leaving
答案:C
John was seen ____ in by the back door, but nobody saw him ___.
A.to come…to leave
B.come… leave
C.to come… leave
D.come…leaving
答案:C