Chinese Test: How to say “God knows” in Chinese?

Beginner Level 初级 (chūjí)

Conversation:

It is Friday and it has been raining all day. However, Lisa and Emily plan to go out on the weekend.          Zhè yǔ yào xià dao shénme shíhou ya?   Lisa: 这雨 要     下 到      什么       时候   呀?

          Guǐ zhīdao, zài …