题干
.
A terrible accident _______,however, occur the other day and we caught sight of it _______ accident.
A terrible accident _______,however, occur the other day and we caught sight of it _______ accident.
A：does; by
B：did; by
C：has to; o
D：had to; on
答案(点此获取答案解析）
B
， 
，则（ ）.