Spreadsheets (BPP MA1 P&R Kit Ch9 Q9.2 p55)

Hello,
The following question has confused me:

In MS Excel, which of the following would NOT correctly perform the calculation required in cell B17 (assuming the rest of the spreadsheet is complete) ?

A = B4-SUM(B7:B15)
B = SUM(C17:E17)
C = B4-B7-B8-B9-B10-B11-B12-B13-B14-B15
D = SUM (C4:E4) – SUM (C7:E16)

My apologies in advance. It’s difficult to explain everything on a spreadsheet question without using screenshots.
If anybody needs further details please ask me. I will try my best to explain or provide them. Thank you.