Which of these has been shown to improve intellectual performance for low-performing children?

On average, the intelligence test scores of the Wallonians are much higher than those of the Danasians. The difference in the average test scores of the two groups might be a product of:

a. genetic differences between two groups with similar environments. b. environmental differences between two groups with similar genetics. c. both genetic and environmental differences between the two groups. d. any of the above.

When alleles in a chromosome pair are identical, they are said to be

a. recessive. c. heterozygous. b. dominant. d. homozygous.