Find the maximum value of x so that 74185x4 is exactly divisible by 4.

Divisibility rule for 4: A number is divisible by 4 if and only if the number formed by its last two digits is divisible by 4.

1. The given number is 74185x4; its last two digits form the two-digit number "x4", which equals 10x + 4.

2. For divisibility by 4, 10x + 4 must be divisible by 4. Since 4 is already a multiple of 4, this simplifies to 10x being divisible by 4, which holds whenever x is an even digit.

3. Testing the even digits available among the given choices, x = 2, 4, 6, 8, each makes the last two digits (24, 44, 64, 84) divisible by 4.

4. Among these, the largest value of x is 8.

Cross-check: Directly dividing 84 by 4 gives 21 exactly, confirming that x = 8 satisfies the condition, and it is the greatest digit among the options for which the rule holds.