——How much did this set of furniture cost?
——I forgot（ ）.
A、
how much it costs
B、
how much did it cost
C、
how much it cost
D、
how much does it cost
【正确答案】：C
【题目解析】：
本题考查宾语从句的语序。
forgot后接宾语从句，宾语从句需用陈述语序。句子时态为一般过去时，从句也应使用一般过去时。故C选项符合题意。
句意：——这套家具多少钱？
——我忘了多少钱。