问题
No one can answer the question _______ we can complete the task in time, do you know? — Yes, and this is because we don’t know the way _______ the scientist used last time．
A:whether; which
B:if; which
C:whether; in which
D:if; in which
B:if; which
C:whether; in which
D:if; in which
正确答案是：
