Factor Check by Multiplying $a(r+s+t)$ B) $a(r-s+t)$ C) $r(a-s+t)$ D) $\operatorname{ar}(1-s+t)$

Factor. Check by multiplying.
-ar - as + at

A) $a(r+s+t)$
B) $a(r-s+t)$
C) $r(a-s+t)$
D) $\operatorname{ar}(1-s+t)$