Melissa：我們身邊有不少商務旅客、外籍同事，甚至來香港參加東亞運動會的健兒，如果他們遇上惡劣天氣，真的會很狼狽。

Venny：是呀！ 考一下Laura看她知道多少。When we have heavy rainfall, what should we do?

Laura：If a black rainstorm warning is in force, you will have to stay indoors until it's lifted.

Melissa：‘in force’ ...