问一道F3的题 following, customer, purchase, account, balance

jasonsg

The debit side of a trial balance totals $50 more than the credit side. Which one of the following could this
be due to?
A a purchase of goods for $50 being omitted from the supplier's account
B a sale of goods for $50 being omitted from the customer's account
C an invoice of $25 for electricity being credited to the electricity account
D a receipt for $50 from a customer being omitted from the cash book

答案是A, 有谁能解释一下？
答案中说D不影响trial balance 的 debit and credit side, 为什么呢？

zhangyuj

...没有上课吗？这个是很基本的东西