Final answer:
The correct answer is 'does / catch'. In the sentence, the subject 'Helen' is a third-person singular noun, so the verb 'catch' needs to be in the present tense third-person singular form, which is 'catches'.
Step-by-step explanation:
The correct answer is does / catch.
In the sentence, the subject 'Helen' is a third-person singular noun, so the verb 'catch' needs to be in the present tense third-person singular form, which is 'catches'. Therefore, the correct sentence is 'What time does Helen catch the bus?'