Select the most appropriate option to fill in blank number

Explanation

The sentence should read: “you had to slow down your own pace to suit his.” The word “pace” means the speed or rate of movement, which fits the context of walking at a speed that matches Ari’s. The other options are incorrect: (1) piece refers to a part of something, (2) peace means tranquillity or calmness, and (4) space refers to an area or distance, none of these options fits in the context of adjusting walking speed.