Question

ustedes type answer... a la fiesta. (ir)

Explanation:

<pre_analysis>
{
"quality": "clear",
"question_count": 1,
"skills_matched": [
"step_cot",
"blank_filling_formatter",
"explain_then_answer",
"quick"
],
"needs_drawing": false,
"concepts_used": [],
"new_concepts": [],
"current_concepts": [
"Spanish Verb Conjugation",
"Irregular Verbs",
"Spanish Present Tense"
]
}
</pre_analysis>

<reasoning>

Identify the subject pronoun and infinitive verb

The subject pronoun is "Ustedes" (you all) and the infinitive verb to conjugate is "ir" (to go) in the present tense.

Conjugate the irregular verb

The present tense conjugation of the highly irregular verb "ir" for the third-person plural pronoun "ustedes" is "van".
</reasoning>

<answer>
Ustedes <blank>van</blank> a la fiesta. (ir)
</answer>

<post_analysis>
{
"subject": "Others",
"question_type": "Fill-in-the-blank",
"knowledge_point": [
"Others",
"Spanish",
"Spanish Verb Conjugation"
]
}
</post_analysis>

Answer:

<pre_analysis>
{
"quality": "clear",
"question_count": 1,
"skills_matched": [
"step_cot",
"blank_filling_formatter",
"explain_then_answer",
"quick"
],
"needs_drawing": false,
"concepts_used": [],
"new_concepts": [],
"current_concepts": [
"Spanish Verb Conjugation",
"Irregular Verbs",
"Spanish Present Tense"
]
}
</pre_analysis>

<reasoning>

Identify the subject pronoun and infinitive verb

The subject pronoun is "Ustedes" (you all) and the infinitive verb to conjugate is "ir" (to go) in the present tense.

Conjugate the irregular verb

The present tense conjugation of the highly irregular verb "ir" for the third-person plural pronoun "ustedes" is "van".
</reasoning>

<answer>
Ustedes <blank>van</blank> a la fiesta. (ir)
</answer>

<post_analysis>
{
"subject": "Others",
"question_type": "Fill-in-the-blank",
"knowledge_point": [
"Others",
"Spanish",
"Spanish Verb Conjugation"
]
}
</post_analysis>