For general graph, how one can get rid of repeated states?

Question

Q:

For general graph, how one can get rid of repeated states?

(a) By maintaining a list of visited vertices

(b) By maintaining a list of traversed edges

(c) By maintaining a list of non-visited vertices

(d) By maintaining a list of non-traversed edges

This question was posed to me in an interview for internship.

Query is from Uninformed Search and Exploration topic in chapter Problem Solving of Artificial Intelligence

Select the correct answer from above options

Interview Questions and Answers, Database Interview Questions and Answers for Freshers and Experience

Answer 1

Correct choice is (a) By maintaining a list of visited vertices

Best explanation: Other techniques are costly.