Trade payables payment period

Which of the following is likely to reduce the trade payables payment period?

A Paying trade suppliers within seven days of reciept of invoice to obtain a discount

B Buying an increasing volume of credit purchases during an accounting period

Sir the correct answer was A
I was wondering why isn’t B the answer because in the formula for trade payable period it is.
(trade payables/credit purchases )*365

so if credit purchases changes then trade payable period also could change right???