In an Effort to Identify the Influence of Genetic Factors

In an effort to identify the influence of genetic factors on both Type 1 diabetes and Type II diabetes, researchers calculated concordance rates for monozygotic twins. Concordance rates of 30-50% have been found for Type I diabetes with concordance rates of 80% for Type II. For both kinds of diabetes, dizygotic concordance rates were about 15%. What does this information suggest concerning the relative effect of genetic and environmental factors for each type of diabetes?

A) Genetic factors have little or no role in the occurrence of Type I diabetes.
B) Type II diabetes is primarily determined by nongenetic factors.
C) Genetic influences exert a larger role in Type II diabetes than in Type I diabetes.
D) Type II diabetes appears to be caused by a single unidentified gene.
E) Environmental factors have no role in the occurrence of either type of diabetes.