Question

how does geographic isolation contribute to speciation?
by changing the amount of gametes the species produces
by making it more difficult for mating to occur because of the size variation in the species
by changing the time of the year when breeding in the species takes place
by making it more difficult for members of the species to locate each other.

Explanation:

Geographic isolation physically separates populations, preventing interbreeding because members can't find each other. Over time, genetic differences accumulate, leading to speciation. The other options describe different isolation types (gamete, size, temporal) not geographic.

Answer:

by making it more difficult for members of the species to locate each other.