The hypothesis asserts that African-Americans are more prone to diseases such as pyelonephritis and syphilis that may result in secondary hypertension.

Associated disorder

Explanation:

Associated disorder hypothesis proposes that the high-frequency hypertension of African-Americans is caused by other diseases such as pyelonephritis and syphilis. There are other hypotheses that can explain the cause too. The genetic hypothesis said that it because the gene of African-Americans is different. The psychological stress hypothesis thinks that discrimination causes stress which leads to higher blood pressure.  

the correct answer, according to e2020, is the second choice there is an occluded front in region a and a cold front in region b.