Correct option is D
Given:
A group of students is seated in a straight row watching a concert.
Dinesh is in the fifth seat from the left.
Nimesh is in the ninth seat from the left.
According to the given information, linear seating arrangement will be-

Lets check by options;
Option (a): There are four students between Dinesh and Nimesh.
3 students sit between Dinesh and Nimesh.
Option (b): Rajesh sits sixth from the left and immediate right of Dinesh.

This is consistent, but it does not directly help us determine the total number of students in the row.
Option (c): Satish sits eighth from the left and immediate left of Nimesh.

This is consistent, but it does not directly help us determine the total number of students in the row.
Option (d): Pritesh sits seventh from the right and there is one student between him and Dinesh.

So, total 13 students in raw.
Thus, the correct answer is (d).