Answer: Option B
:
B
Suppose we draw $PM$ such that the angle $\angle QPM$ is an obtuse angle. Next we mark $(m+n)$ arcs on the ray PM such that $P{P}_1$ = $P_1{P}_2$ = $P_2{P}_3$ = … = $P_{m+n-1}$$P_{m+n}$.
For our convenience let us assume $m+n=5$ so we can explain things much easier. (In our case the required ratio could be 1:4 or 2:3 or 3:2 or 4:1 etc...)
Now in the $△$$QP{P}_5$,
If, $\angle$$QP{P}_5$ is obtuse then $\angle$$Q{P}_{5}P$ and $\angle$$PQ{P}_5$ would become very small (compared to the case where $\angle$ $QP{P}_5$ is acute) and it would be difficult to draw a line parallel to $Q{P}_5$ (Because small angles and hence small radii of arcs are involved in construction of parallel lines)
This will make drawing of parallel lines very congested compared to drawing parallel lines on line segment PN with acute angle $\angle QPN$.

You can see from the diagram that $P_4{Q}^{\prime }\parallel P_{5}Q$ is more closely spaced compared to$P_4^{\prime }{Q}^{\prime }\parallel P_5^{\prime }Q$.
So we prefer to draw an acute angle to make it more clear and spacious i.e. to avoid congestion.