If J is the sister of K. K is the sister of L. L is the sister of M. M is the brother of N. Then which of the following statements is not necessary true? (A) K and L are sisters. (B) M and N are broth

Question

If J is the sister of K. K is the sister of L. L is the sister of M. M is the brother of N. Then which of the following statements is not necessary true? (A) K and L are sisters. (B) M and N are brothers. (C) L is sister of N. (D) J, K, L are females and M is male. Choose the correct answer from the options given below:

FirstInTest · Accepted Answer

Correct answer: B. Let's deduce relationships and genders:
1. J is sister of K $\Rightarrow$ J = female.
2. K is sister of L $\Rightarrow$ K = female. L's gender is unknown (can be male or female).
3. L is sister of M $\Rightarrow$ L = female. M's gender is unknown (can be male or female).
4. M is brother of N $\Rightarrow$ M = male. N's gender is unknown (can be male or female).

From these, we have: J=female, K=female, L=female, M=male. N's gender is still unknown.

Now check the statements:
(A) K and L are sisters: K=female, L=female. This is True (necessary).
(B) M and N are brothers: M=male, but N's gender is not given. N could be a sister. So, this is Not necessarily true.
(C) L is sister of N: L=female. M is brother of N, and L is sister of M, so L and N are siblings. L is female. This is True (necessary).
(D) J, K, L are females and M is male: J=female, K=female, L=female, M=male. This is True (necessary).

The statement that is not necessarily true is (B).

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