Trent knows that 1 pint equals 16 fluid ounces. His punch recipe calls for 3 pints of pineapple juice.

C. 32 ounces (3 pints x 16 fluid ounces per pint = 48 fluid ounces)

To find out how many fluid ounces of pineapple juice Trent needs, we need to multiply the number of pints by the conversion factor of 16 fluid ounces per pint.

Trent needs 3 pints of pineapple juice.

3 pints * 16 fluid ounces/pint = 48 fluid ounces

So, the answer is D. 48 ounces.