Let's analyze all the options:
The distance they rode increases for the entire ride (False) you can see a horizontal line which means the distance stopped.
The club members stopped for a rest during the ride (true, that's why there is a horizontal line, where distance doesn't change and time goes on)
The club members rode their bikes 6 miles (FALSE, they rode for 6 hours, but the distance in miles is longer)
The club members rode at a constant speed (FALSE, if it were true, the line would be completely diagonal)
