Our government has taken some measures to overcome the lack of electricity, but it may take some time ________ we have enough power.
A．since
B．after
C．unless
D．before
Our government has taken some measures to overcome the lack of electricity, but it may take some time ________ we have enough power.
A．since
B．after
C．unless
D．before
D解析：句意：我们的政府已经采取了一些措施来克服电力短缺，但是可能还需要一些时间我们才能拥有足够的电能。since “自从，既然”；after “在……之后”；unless “除非”；before “在……之前”。根据句意，选择D项。