Much to the couple’s comfort ,their income is know double _____it was five years ago请问为什么?

Much to the couple’s comfort ,their income is know double _____it was five years ago请问为什么?
Much to the couple’s comfort ,their income is know double _____it was five years ago
请问为什么?

Much to the couple’s comfort ,their income is know double _____it was five years ago请问为什么?
D是what 你都忘贴上了
若是如此,分析如下:
全句应为：Much to the couple’s comfort ,their income is know double what it was five years ago.
句意为“很让这对情侣高兴的是,他们现在的收入已经是5年前的两倍了”
其中what it was five years ago为名词性从句,指代情侣5年前的收入