Answer:
Option A, The lizards on one side of the mountain were exposed to different conditions and therefore different characteristics were selected.
Step-by-step explanation:
The lizards population got divided into two parts due to development of mountain in a given sphere. There are high chances that the resources in this sphere were unevenly distributed due to which none of the population of lizard was able to use all the resources (in the manner they used earlier) after development of physical barrier. Due to this, the lizards now are forced to live either with limited resources/or they are exposed to some new resources (which they did not explored earlier in the same sphere when it was united) leading to evolution of new species of lizard.
Hence option A, is correct.