💡 Detailed Explanation
The correct choice is 'ために' (for the sake of / in order to). The grammar pattern '[Verb Dictionary Form] + ために' indicates a conscious purpose or goal of the speaker, where the verb is controllable (entering college is an active goal). Sentence translation: 'I am studying hard in order to enter college.' 'ように' (in order that / so that) is used for non-controllable verbs, potential forms, or negative forms (e.g., '入れるように'). 'ことに' and 'ものに' do not express purpose.