All the apparatus______ before the experiment began.1.have been tested 2.had been tested

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All the apparatus______ before the experiment began.1.have been tested 2.had been tested

All the apparatus______ before the experiment began.1.have been tested 2.had been tested
All the apparatus______ before the experiment began.1.have been tested 2.had been tested

All the apparatus______ before the experiment began.1.have been tested 2.had been tested
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