The different forms a gene may have for a trait are called alleles. Blood type is an example of alleles. They determine the hereditary characteristics an offspring gains from their parents.
It breaks down lactose into the galactose and glucose. So the answer here is C.
This can affect the organisms living there because now, their environment is probably different than what they have been living in for a long time, so now they have to adapt to this new environment, and if they don't, the organisms will probably end up dying.
