What makes Jillian a good team manager in BASKETBALL BLUES

the answer is “ she tends to keep close track of details” :)

Explanation:

Hi! Your answer is B. a semicolon

Here's why:
A. hyphen/dash- it doesn't make sense.
B. It's the correct answer. They are two independent clauses, and semicolons combine those sentences into one. 
C. Dashes are used for lists. Not independent clauses. 
D. Commas won't work, UNLESS you add something else, maybe. depends on what you add. But since that isn't a choice, it's b. 

Hoped I helped!
-Dawn