问题
选择题
With some technical problems to be solved, it may be a while the system is put into use.
A．when
B．after
C．since
D．before
答案
答案：D
句意：有一些技术问题要解决，所以在这个系统投产前还需一段时间。所以选D。
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With some technical problems to be solved, it may be a while the system is put into use.
A．when
B．after
C．since
D．before
答案：D
句意：有一些技术问题要解决，所以在这个系统投产前还需一段时间。所以选D。