不良饮食可能引起疲劳，但我不认为这里情况如此。

Bad diet can cause tiredness, but I don't think that ___is ___the ___case here.

我猜想价格包含早餐——如果不是这样，请告诉我们。

I take it that the price includes breakfast - if that ___isn't ___the ___case, please let us know.

你能告诉我你是否会及时回来吃晚饭吗？如果是这样，我会为我们做一顿特别的晚餐。

Could you please let me know if you'll be back in time for dinner? If that ___is ___the ___case, I'll make a special dinner for us.