Amechanism of darwin's proposed theory is
a. natural selection
c. variation
b. over production of offspring
d. all of these

The answer is a. natural selection.

In natural selection, genotype variations that will increase the chance of survival and reproduction of some organism are preserved and will be inherited. Darwin's theory suggested that there are variations among individuals in a population and that these variations will help individuals to survive. According to Darwin, natural selection is the only factor that affects frequency of different variations.

b

is correct hope this   also i learnd this in middle school

the second type of galaxy is called a barred spiral, which has a thing called a bar straddling the nucleus