is the case|is not the case

不良饮食可能导致疲劳，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.

您能否也告诉我您是否会及时回来吃晚餐，因为如果是那样的话，我会为我们做一顿丰盛的晚餐。

Could you also please let me know if you're coming back in time for dinner because if that ___is ___the ___case, I'll make a splendid dinner for us.

我猜想预订包含早餐——如果不是这样，请告知我们。

I take it that the booking includes breakfast - if that ___is ___not ___the ___case, please let us know.