if p,q,r and s are to be distinct, then a,b,c, and d need to be even (because when a perfect square is expressed in terms of prime factors, they all should have even powers)
thus question rephrased, are a,b,c,and d even?

statement 1. 18 is factor of ab and cd. not sufficient as this does not tell us about individually a and b & c and d being even or not.

statement 2. 4 is not a factor of ab and cd. that means either of a , b & either of c , d is not even thus sufficient to answer the question posed above!

hence the answer B

hi anderson,

can u explain stmtn 2 with an example using numbers?

minor correction!! re read the statement 2!

only means that: if 4 is not a factor of ab, both a and b together can not be even. say a=2 and b=3 4 is not a factor of 6. but if a=2x (even) and b= 2y(even) =>4 has to be factor of ab.