Please answer a question about the following article about Boston:

The area's many colleges and universities are active in college athletics. Four NCAA Division I members play in the city—Boston College, Boston University, Harvard University, and Northeastern University. Of the four, only Boston College participates in college football at the highest level, the Football Bowl Subdivision. Harvard participates in the second-highest level, the Football Championship Subdivision.

How many NCAA Division I members play in Boston?
four