Which of the Following Does NOT Represent Stratification in the United

Which of the following does NOT represent stratification in the United States?

A) Before the abolition of slavery,the United States was a racial caste system because unless a slave escaped or was freed by his or her owner,it was usually a permanent condition.
B) Class stratification resembles a teardrop,with a large number of people in the middle ranks,a slightly smaller number of people at the bottom,and very few people at the top.
C) It is relatively easy to move upward from working class to upper class,as long as you earn an education and work hard.
D) Many middle-class Americans have experienced downward mobility in recent decades.