Which card must be played towards a 31?

Scenario:

The score is 24, and one player says go. The other person holds a 3 and a 5 in their hand but wants to hold onto the 5 for the next round. Are they obligated to play their highest card towards 31 or can they choose to play the 3?

You Decide

You can play whatever card you want as long as you play one or both depending on the score. In this case you would want to play the 3, take your point and hope they play a ten card so you can get more points.

They can play the card of

They can play the card of their choice.