F3 Suspense Account BBP Rev Kit

Hi John,
The following question is about suspense accounts.
A company’s trial balance totals were:

Debit $ 387,642
Credit $ 379,511

A suspense account was opened for the difference.

Which one of the following errors would have the effect of reducing the difference when corrected?

A. The petty cash balance of $ 500 has been omitted from the trial balance.
B. $ 4,000 received for rent of part of the office has been correctly recorded in the cash book and debited to rent account.
C. $ 3,000 paid for repairs to plant has been debited to the plane asset accounts.
D. An invoice for Mr. A Smith for $ 400 has been posted to the account of Mrs B Smith in error.

How is the answer D? I don’t understand the workings. If you could please help.