I think "if" is possible, but it is unlikely, and some of us think "if" for "whether" is a mistake in this context. Mary: Did Dad tell you if he is going to Taipei 101 next week? Sally: Yes, Dad told me if he is going to Taipei 101 next week.
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WenwenWhy can we use "whether" instead? Are they different? I thought they were the same.The usage note from the American Heritage Dictionary under "if" says it better than I could: