Final answer:
The verb 'caer' conjugates to 'caigas' in the subjunctive, 'tu' form. The subjunctive form in Spanish is used to express situations like doubt, possibility or actions that have not yet occurred.
Step-by-step explanation:
The verb caer in the subjunctive form for tu (you, informal singular) conjugates to caigas. The subjunctive form is often used in Spanish to express doubt, possibility, necessity, or action that has not yet occurred. So, when you are using 'caer' in a context requiring the (tu) subjunctive form, use 'caigas'. For example, in the sentence 'Es posible que tú caigas,' meaning 'It's possible that you fall,' 'caigas' is the correct form to use.
Learn more about Subjunctive conjugation