问题补充：
and we’ll finish the work ahead of time.
A. An hour earlier
B. If we start an hour earlier
C. Starting an hour earlier
D. Started an hour earlier
答案：
(答案→)A. An hour earlier
B. If we start an hour earlier
C. Starting an hour earlier
D. Started an hour earlier
解析：考查特殊句式。本题是由特殊句式：祈使句+连词+陈述句，转换而来。祈使句+连词+陈述句=If引导的条件句+主句。这个句型进一步转换成：名词短语+连词+陈述句。本题：An hour earlier，and we’ll finish the work ahead of time.=If we state an hour earlier, we’ll finish the work ahead of time.故A正确。
