Research Suggests Which of the Following About Mathematics Textbooks

Research suggests which of the following about mathematics textbooks?

A) They tend to include more concepts per sentence but fewer per paragraph than books from other content areas.
B) They tend to include fewer concepts per sentence but more per paragraph than books from other content areas.
C) They tend to include about the same number of concepts per sentence and per paragraph than books from other content areas.
D) They tend to include more concepts per sentence and more concepts per paragraph than books from other content areas.
E) They tend to include fewer concepts per sentence and fewer per paragraph than books from other content areas.