Which natural occurrence is an example of a long-term environmental change?

Lightning sparks a forest fire.
An earthquake results in a tsunami.
A river floods due to a strong thunderstorm.
The peppered moth evolves from a light to a dark color.

What was the purpose of mendel's experiments with dihybrid crosses? a. to determine if dna was a transforming factor b. to determine if traits could be recessive c. to determine if traits affected each other d. to determine if traits had more than one allele