Final answer:
The AI function 'getplay' should return the smallest-rank valid card from a hand in a card game, resolving ties arbitrarily since there is no tie-break policy.
Step-by-step explanation:
The public card getplay(hand hand, cardpile cardpile) function in an AI class within a card game context should return the card with the smallest-rank that is still valid to play. If there happens to be more than one card with the same smallest rank, breaking the tie can be done arbitrarily as there is no specific policy required for which card to choose. The answer is D. the smallest-rank valid card.