A. Though personally, I think "Yes, you can" sounds a bit stiff.
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CalifJimHela,
The use of "could" to mean "can"* is not possible in that context - an "assertive" context.
The use of "could" to mean "can"* in such contexts is restricted to "non-assertive" contexts, e.g., negations and questions.
[ What is true of the "could"/"can" pair in this respect is generally true of the "mi