Explanation:

- To find the smallest number to add to 888 for it to be divisible by 35, first calculate the remainder of 888 divided by 35.

- Dividing 888 by 35 gives a quotient of 25 and a remainder of 13.

- The number needed to add to 888 is the difference between 35 and the remainder, which is 35 - 13 = 22.

Option:1 - 22

- Adding 22 to 888 gives 910, which is divisible by 35.

Option:2 - 23

- Adding 23 gives 911, not divisible by 35.

Option:3 - 20

- Adding 20 gives 908, not divisible by 35.

Option:4 - 21

- Adding 21 gives 909, not divisible by 35.