Final answer:
The largest 5-digit number that is a multiple of both 4 and 9 is 99972, as it meets the divisibility tests for both numbers.
Step-by-step explanation:
The question asks for the largest 5-digit number that is a multiple of both 4 and 9. To be a multiple of 4, a number must have its last two digits be a multiple of 4. To be a multiple of 9, the sum of the number's digits must be a multiple of 9. Among the choices, only 99972 is divisible by both 4 and 9. The divisibility test for 4 confirms that 72 is a multiple of 4, and adding the individual digits of 99972 (9+9+9+7+2 = 36) shows that the sum is a multiple of 9. Therefore, the largest 5-digit number that satisfies the conditions is 99972.