Final answer:
The expression to find the product of 320 is '32 * 10'. This is the most straightforward option representing the number 320 with its factors.
Step-by-step explanation:
The expression that can be used to find the product of 320 is 32 * 10. To verify this, we can multiply each pair of numbers in the given options and see which one equals 320:
8 * 40 = 320
16 * 20 = 320
64 * 5 = 320
32 * 10 = 320
As we can see, all options except for 64 * 5 actually yield the product of 320. However, since we're looking to provide correct option in final answer, the most straightforward option is d) 32 * 10, which immediately reflects the number 320 in its factors.