Khi A thì B

Explain:

Used to link two clauses that have relation of condition and result in a compound sentence. A express the condition. B express the result.

Example:

Khi mùa Xuân đến thì cả khu rừng này đầy hoa.
When spring comes, this forest is full of flowers.
Khi tôi lớn thì bà tôi không còn nữa.
When I grew up, my grandmother was gone.