If we employ a broad definition of what is urban - that is, one that includes suburbs - about 33,000 square miles of land in the United States were converted from rural to urban uses in the 1960's and 1970·s.

The above information is a statistic. We do not know precisely if 60's and 70? comprise for two decades or years during.
Nonetheless, We do have only the definition of what is "urban= 33,000 miles.

Assume that in two decade the increase is basically 66,000. Thius is just to give you an idea


From 1960 to 1980 the area of urban settlement increased by 84 percent while the urban population increased by 33 percent.

From 60's to 80's we did have an increase of 84% which means that if the starting point was 33,000 we did end up with 60,720 miles BUT the population in 30 years grew only 33 %. Seeing this way clearly the area in not overcrowded

If all of the statements above are true, which of the following must also be true?

(A) The rate of growth of the population in urban areas in the United States increased between 1960 and 1980.

Just a fact

(B) By 1980 the fraction of the United States population living in urban settlements built after 1960 exceeded the fraction of the population living in urban settlements built before 1960.

Exceded fraction. What is NOT we are looking for

(C) The density of the urban population in the United States decreased between 1960 and 1980.

Correct

(D) Areas in the United States that were definitely urban before 1960 gained population at the expense of rural and formerly rural areas between 1960 and 1980.

What was before is irrelevant

(E) The population of rural areas decreased between 1960 and 1980.

We do not know. We do know only it increased and not proportionally