Sentence Correction (SC) | As the cost of wireless service has steadily dropped over

In Option C, if we change this highlighted portion
phones by using their mobile phones to make long-distance calls at night or on weekends, when

and convert this option into the following sentence(this change taken from option D)
phones by using their mobile phones to make long-distance calls during the night or weekends, when

Will both the versions be correct?

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