Correct Answer: M @ G $ K

Solution : Given:
A @ B means A is the son of B.
A $ B means A is the sister of B.

Let's check the options –
First option: M $ G @ K
According to the given information, the family tree will be –

.
From the above family tree, it is evident that here M is female.
Second option: K @ G $ M
According to the given information, the family tree will be –

From the above family tree, it is evident that the gender of M is not defined.
Third option: G @ K $ M
According to the given information, the family tree will be –

From the above family tree, it is evident that the gender of M is not defined.
Fourth option: M @ G $ K
According to the given information, the family tree will be –

From the above family tree, it's clear that M is K's sister's son.
Here, the quadrilateral represents the male and the circular figure represents the female in the figure.

So, only the fourth option fulfills the relation as per the family tree. Hence, the fourth option is correct.