Answer
a) is correct.
Work Step by Step
The positive direction is along the direction of the canoe. Therefore, person 1, diving off to the back, must have a negative momentum while person 2 must still have a positive momentum. Eliminate c) and d).
According to conservation of total linear momentum, $$\vec{p_{f1}}+\vec{p_{f2}}=\vec{p_i}=+110m/s$$
Using this equation, we can see that a) is correct.
