Find the smallest multiple of $$7$$ that is greater than or equal to $$20 $$. 
Overseas Competition->Knowledge Point->Number Theory Modules->Factors and Multiples->Basic Concepts of Factors and Multiples
$$2\times7=14$$, $$3\times7=21$$, since $$14$$ is smaller than $$20$$ and $$21$$ is the closest multiple of $$7$$ and greater than $$20$$, we choose $$\text B$$. 