23.The couple finally bought the car they liked after they ______ up for a whole year. （ ）
A
were saving
B
have saved
C
would save
D
had saved（时态，过去完成时）
过去完成时基本词形变化：had+过去分词。
分析句子时态可知，买车是过去式，攒了一年的钱发生在过去的过去，因此用过去完成时。句意：在攒了一年钱以后，这对夫妇终于买了他们喜欢的车。
易用成完成时，和过去完成时混淆。