Understudying
v. 练习做临时演员( understudy的现在分词 )
🗣️ 情景例句
What's my account balance?
我的户头还剩多少钱？
Know something like the palm of one's hand.
熟知其事，了如指掌。
I think you probably know China has adopted a flexible policy in her foreign trade.
我想你也许已经了解到中国在对外贸易中采取了灵活的政策。