Short explanation: We use "Do" to form a question in the present simple tense when the subject is "you" and the main verb is "go".
Step-by-step solution:
- The sentence is a question in the present simple tense, indicated by "often".
- The subject is "you", and the main verb is "go".
- The auxiliary verb for "you" in the present simple tense is "Do".
Answer: Do you often go to the zoo?