---you can't imagine ___ fantastic fun web chatting is.---really?but it may cause a lot of trouble sometimes.a whatb howc whyd so为什么选C?这句话怎么翻译?

---you can't imagine ___ fantastic fun web chatting is.
---really?but it may cause a lot of trouble sometimes.
a what
b how
c why
d so
为什么选C?这句话怎么翻译?

应该选A what
what 修饰名词fun
你想象不出网络聊天是多么的奇妙.
真的吗?但有时侯也可能会引起麻烦.