In a team, if all members do regular check-in of the code, then how should one ensure that the code is not broken anywhere?

Question

Q:

In a team, if all members do regular check-in of the code, then how should one ensure that the code is not broken anywhere?

Through SCM triggered build 

Through scheduled build

By triggering automated build after check-in

Through SCM based code branching

Answer 1

Through SCM triggered build