If $$a$$, $$b$$ are prime numbers, and $$3a+7b=41$$, then $$a+b=$$． 
Overseas Competition->Knowledge Point->Number Theory Modules->Prime and Composite Numbers->Applying Special Prime Numbers
Based on the laws relating to the parity in addition and multiplication, either $$a$$ or $$b$$ must be $$2$$. If $$a = 2$$, then $$b = 5$$, and $$a + b = 7$$; if $$b = 2$$, then $$a = 9$$; $$9$$ is not a prime number, which doesn\textquotesingle t match the conditions in the question. Therefore, we choose B. 