In English, the phrase "rely on" means to depend on or trust someone or something. Therefore, the correct choice here is option (1) on.
- Option (2) the does not fit grammatically, as the verb "rely" requires the preposition "on".
- Option (3) to is incorrect because "rely" is not followed by "to" in this context.
- Option (4) with is also incorrect because the preposition "with" is not commonly used after "rely" in the sense of depending or trusting.
Thus, the correct answer is option (1).