To solve the problem, we must analyze the family relationships described:
- Golu is the son of Molu.
- Molu and Polu are sisters. This implies that they share the same mother.
- Pillu is the mother of Polu. This means Pillu is also the mother of Molu. Therefore, Pillu is the grandmother of Golu.
- Gannu is the son of Pillu, making Gannu the brother of both Molu and Polu, since Pillu is their mother.
Now let's evaluate the statements:
- Golu and Gannu are cousins: This is not possible because Golu is the nephew of Gannu.
- Golu's nephew is Gannu: This is incorrect because Golu is younger than Gannu, and Gannu is Golu's uncle.
- Golu's maternal uncle is Gannu: This is correct because Gannu, being the brother of Molu (Golu's mother), is indeed Golu's maternal uncle.
- None of the option is correct: This is incorrect because the third option is true.
Hence, the statement that is definitely true is:
Golu's maternal uncle is Gannu.