Theory: LCM of two numbers is >= to the greater of the two number and <= product of the two number.

Greater(a,b) <= LCM(a,b) <= a*b

So, LCM(k,n) <= k*n
It will be equal to k,n only when k and n are co-prime numbers. (means they don't have any common factor apart from 1)

Since, we don't know the value of k and n so we cannot determine the answer.

Some, mathematical examples
Ex 1: if k= 2 and n = 3 then LCM(2,3) = 6
=> LCM(k,n) = k*n

Ex 2: if k= 2 and n = 4 then LCM(2,4) = 4
=> LCM(k,n) <= k*n

So, answer will be D
Hope it helps!

To learn more about LCM and GCD watch the following videos

mrr0821 Least multiple of 2 & 3 will be 6 as they are co-prime numbers. (they don't have any any common factor, apart from 1)