Last Saturday we A on an excursion to the botanical garden with our biology teacher.

The sentence describes a past event, so the past tense of 'go' is required. The options are 'go', 'goes', and 'went'. 'Went' is the correct past tense form.

1. Identify the grammatical context: past event.

2. Evaluate the options: 'go' (present), 'goes' (present, third person singular), 'went' (past).

3. Select the correct past tense form: 'went'.

went