Open gram merely it will surely help you
Answer:

Explanation:
Given sentence,
Sabin slept at 9 pm.
To change this sentence into negative, add did not after the subject .
Sabin <u>did</u><u> </u><u>not</u> sleep at 9 pm.
Note: While changing positive sentences into negative, V² takes did ( V² = did + V¹ )
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