Answer 1:
This is an example of successful adaptive mutation. Adaptive mutations actually happen because of high levels of stress in the organism's environment caused by the same stressor/s. Here, lots of rabbits being excessively cold all the time due to environment changes caused a lot of extra stress and over time, they successfully mutated to adapt to their environment.
Answer 2:
The answer should be the 4th one. A mutation that doesn't work doesn't always fully go away, but it will become much less common.
