$$26+18-38=6$$, $$26-6=20$$. 
There are $$38$$ students in the class. Each student is in either math club or music club or both. Given that among students in this class, $$26$$ students are in the math club, and $$18$$ students are in the music club, there are~\uline{~~~~~~~~~~}~students in the math club only and not in the music club. 
Options:
A: $$18$$ 
B: $$19$$ 
C: $$20$$ 
D: $$21$$ 