Answer:
Speak is the correct grammar for the sentence
Step-by-step explanation:
You can see that by looking at each sentence and see which one makes more sense.
"Can you tell Spanish?" That doesn't make much sense so it's incorrect.
"Can you talk Spanish?" This also doesn't make much sense as you wouldn't say it like this so it's also incorrect.
"Can you speak Spanish?" This one makes the most sense and would be correct!