Question

where is the founder effect most likely to occur?
in the oceans and other connected aquatic habitat
on grasslands and other connected terrestrial habitats
on islands and other isolated habitats that arent connected

Explanation:

The Founder Effect occurs when a small group of individuals establishes a new population, and this new population's gene pool is different from the original population. Isolated habitats like islands have limited gene flow (movement of genes from one population to another). In connected habitats (oceans, grasslands etc.), there is more gene flow. So, isolated habitats are more likely to show the Founder Effect.

Answer:

on islands and other isolated habitats that aren't connected