This issue was magnified in a recent quiz I made, in which the player had to tap the location of a given landmark. A lot of users ended up scoring very badly, despite knowing the location, because the taps weren't precise, and as far as mobile users can go there is not any more precision that can be achieved.
Even personally, when I tried the same quiz on mobile, and knowing exactly where the dots are, I could only get 4 correct out of 20.
A solution that has been suggested by MasterRocket is to have an increase tolerance for mobile users. If you tap within a specific area of the answer while playing on mobile, it would be registered as correct. This helps to keep the target area 'normal' for desktop, where precision is possible, and also helps mobile users.