A particular population of chickens has a frequency for the dominant allele as 0.70 and a frequency for the recessive allele as 0.30. Which expression is the correct way to calculate the frequency of individuals that are heterozygous?

A) (0.70) x (0.30)

B) (0.70) - (0.30)

C)2 x (0.70) x (0.30)

D)2 x (0.70 - 0.30)