Answer:
The options are not shown, so it is kinda hard to give you the exact answer.
But i can try to give a general explanation on the topic.
Interference happens when two waves interact between them. We usually use waves with the same wavelength and same phase.
There are two "main" types of interference:
Destructive interference: Happens when the peak of one wave and the trough of the other wave happen in the same place, then when we add these waves, we have a subtraction, and then the amplitude of the resultant wave is smaller than the amplitudes of the original waves (if both initial waves have the same amplitude, then the amplitude of the resultant wave in that position is zero).
Constructive interference: Similar to the previous case, but now the two waves have the peaks or toughs in the same position, then when we add the waves, we have an addition in the amplitude, then the amplitude of the resultant wave will be larger than the amplitudes of the initial waves.
Then if you are looking for constructive interference, you need to look for an option where the peaks of the waves coincide. For example, in the top image we can see, at the top, a wave with an amplitude of 2 units.
And at the bottom a wave with an amplitude of 1 unit.
We also can see that the peaks (and the tough) are in the same place, then we will have constructive interference. Then the amplitude of the resultant wave will be equal to the sum of the amplitudes of the initial waves (2 and 1)
Then the amplitude of the resultant wave is 2 units + 1 unit = 3 units.
