Mrs Grey preferred to ride a bicycle to work___it was a rainy day ,__it gave her some exercise.47

Mrs Grey preferred to ride a bicycle to work___it was a rainy day ,__it gave her some exercise.47
Mrs Grey preferred to ride a bicycle to work___it was a rainy day ,___it gave her some exercise.
A except ,and
B unless,for
C only if,when
D until,because
要答案和理由
,并解释一下为什么其他答案不可以,最好详细一点
475