If the new safety system _______ to use, the accident would never have happened.
A. |
had been put |
B. |
were put |
C. |
should be put |
D. |
would be put |
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If the new safety system _______ to use, the accident would never have happened.
A. |
had been put |
B. |
were put |
C. |
should be put |
D. |
would be put |