A. Brother B. Uncle C. Cousin D. Father
thanks yash for asking to answer.
it is a pretty simple question from the blood relation.
so let's split the statement in two parts.
1. he is son of ----
2. the only son of my mother.
so on solving part 2 we get that it is suresh himself.
now the problem is
1. he is son of ----
2. suresh.
so here we get to know that it is father son relation. so answer is indeed option D that is suresh is father of that child in the photograph.