Question

Lock the door before---------out

Answer 1

Answer:

going out

Explanation:

kyunki aaj kal vo bahut ho rahe hain

dil pe naa lena jo bhi hooo

Answer 2

The blank can be filled with the word "going"

So the correct sentence will be

Lock the door before going out.

This is a general statement given by someone. He is saying someone that he should lock the door before going out .

As "out" is used here so it gives a sense that someone is going outside. That's why going is used.