She's been working hard _____ two this afternoon.
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since
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for
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about
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none
Reveal answer
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A
Correct answer
Explanation
We use 'since' with a specific point in time (like 'two this afternoon') and 'for' with a duration. The present perfect continuous 'has been working' with 'since' indicates action starting from a precise moment and continuing to the present.
AI explanation
Since is used with a specific point in time (like two o'clock) to mark when a continuous action began, which fits the present perfect continuous has been working. For would be used with a duration (for two hours), not a specific clock time, so it doesn't fit here.