suffer
受损害，受到不良影响  

例句：
Your studies will suffer if you play too much football.
如果你总是踢足球，你的学业就会受到影响。

under the cover of...
在……的掩护下；以……为借口
 
例句：
The troop withdrew safely under the cover of darkness.
军队在夜幕的掩护下安全撤离了。
 

I'll pick up the tab.
我来付帐。

对话：
A: Do we have to pay the transportation fee?
B: No. This trip is on me. You don't have to spend a penny. I'll pick up the tab.
A: How generous you are.

A：我们得付交通费吗？
B：不，这次旅行我请客。你们不用花一分钱。我来付费。
A：你真慷慨。