Ans will be A
Theorem
Let n=p1p2…pk, where the pi are distinct primes.
The Dn is aBoolean algebra.
choice A) n=40 =2x2x2x5 so it is not a boolean algebra ( 2 is repeating) Hence the ans
B) n=66 =2x3x11 so it is boolean algebra (all are distinct)
C)n=210=2x3x5x7 so it is boolean algebra (all are distinct)
D) n=646 =2x323 so it is boolean algebra (all are distinct)