Waves from Two Slits $S$ And $Q$ Will Destructively Interfere and Cancel at a Point

Waves from two slits $S$ and $Q$ will destructively interfere and cancel at a point $P$ if the distance between $P$ and $S$ is larger than the distance between $P$ and $Q$ by

A) $\lambda$
B) $n \lambda$ (where $n$ is an integer)
C) $\frac{1}{2} n \lambda$ (where $n$ is an integer)
D) $\left(n+\frac{1}{2}\right) \lambda$ (where $n$ is an integer)
E) Other (specify)