The default header for a worksheet is:

None............,,.,,.,",.........

I agree, there is no header, it is blank by default, so option D) would be my answer and in agreement with you Fitah.

D. None

because when you open new workbook in excel it will be either book1-excel, and if book1-excel is already open then it will be book2-excel.

depend on the default name set

D. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>None