3 A: Why do you need hot soapy water? B: Because I (wash) the car.

1. The sentence describes a reason for needing hot soapy water, implying an action that is about to happen or is in progress.
2. The verb 'wash' needs to be conjugated to fit the context of 'because I...'.
3. The correct form is 'am going to wash' or 'will wash'.