Subsidiary

Boo is a subsidiary of Betty. At the year end Boo has a current account balance debit balance of $50,000, but Betty has a current account credit balance of only $40,000.
Which of the following two reasons might explain the difference?
1 Boo had posted a cheque for $10,000 to Betty on the last day of the year
2 Betty had posted a cheque for $10,000 to Boo on the last day of the year
3 Betty had despatched $10,000 of inventory to Boo on the last day of the year
4 Boo had despatched $10,000 of inventory to Betty on the last day of the year
A 1 and 3
B 1 and 4
C 2 and 3
D 2 and 4
Correct answer is D..I didnt understand what they mean in this question