What does the exemption method of giving double taxation relief mean?

What does the exemption method of giving double taxation relief mean?
A . The countries agree that all types of income will be exempt or partially exempt in one country or the other.
B . The countries agree on certain types of income which will be exempt or partially exempt in one country or the other.
C . The countries agree on certain types of income which will be exempt or partially exempt in both countries.
D . The countries agree that all types of income will be exempt or partially exempt in both countries.

Answer: B