- 试题详情及答案解析
- By the time Dave reached the small boat, a thick white fog _______ over the surface of the water.
| A．spread | B．has spread |
| C．had spread | D．was spreading |
- 答案：C
- 试题分析：考查时态。句意：by the time...意为“到......的时候”，常与完成时连用，排除A、D；当by the time后跟一般过去时的时候，主句用过去完成时，故选C。
考点：考查时态