Can someone explain the answer to me?

Sample question #1:
The 10-unit office complex consists of 8 two-office suites at $1450/month and two three-office suites at $1575/month. The Smith-Johnson law practice moves into the office complex.

Conclusion:
The Smith-Johnson practice pays $1575/month in rent.
Is this
a. necessarily true.
b. probably, not necessarily true.
c. indeterminable, cannot be determined.
d. probably, not necessarily false.
e. necessarily false.

Answer:
The conclusion is probably, not necessarily false.

I don’t understand because I feel like the answer could be D or B. what’s the difference?