Explanation:

- Conundrum: This word typically means a difficult problem or a puzzling situation that is hard to resolve.

- Option 1, potential: This word refers to the ability or capacity to develop into something in the future. It doesn't align with the meaning of conundrum.

- Option 2, problem: This is the correct synonym for conundrum. Both refer to something that's challenging or difficult to deal with.

- Option 3, fright: This means a sudden feeling of fear or shock, which does not connect to the idea of a complex problem.

- Option 4, confidence: This involves having self-assurance or belief in one's abilities, quite unrelated to the meaning of conundrum.