If 5x^2 has two different prime factors, at most how many different prime factors does x have?  Choose one
A) 1  B) 2  C) 3  D) 4  E) 5
x cannot have more than 2 prime factors, because in this case 5x^2 would also have more than 2 prime factors.   Can x have 2 prime factors? Yes, consider x=2*5= 
<gadget id="calculator">2*5</gadget>
<output>10</output>
10 (in this case 5x^2 still has 2 prime factors).   Answer: 2.
<result>B</result>
If 5x^2 has two different prime factors, at most how many different prime factors does x have?