The $$3$$ prime numbers between $$40$$ and $$50$$ are $$41$$, $$43$$, and $$47$$. 
There are exactly $$3$$ prime numbers between． 
1: $$10$$ and $$20 $$ 
2: $$20$$ and $$30$$ 
3: $$30$$ and $$40$$ 
4: $$40$$ and $$50$$ 