I.不定式时态构成及用法
1. 一般式：其表示的动作通常与谓语所表示的动作或状态同时（或几乎同时）发生，或在它之后发生；其形式为：主动 to do sth／被动 to be done
I'm glad to meet you.
I'd like to be told what's going on.
2.进行式：其表示动作正在进行，与谓语动词表示的动作同时发生；其形式为：to be doing
To be cycling in a sandstorm is frightening.
They are said to be building another bridge across the Changjiang River.
They pretended ______________________(work hard ) when their boss passed them.
