I prefer to ride my bike _____ the hill.
I prefer to ride my bike _____ the hill.
Explanation
When moving from a higher place to a lower place, we use "down" (e.g., ride down the hill).
So, "I prefer to ride my bike down the hill" is correct.
When moving from a higher place to a lower place, we use "down" (e.g., ride down the hill).
So, "I prefer to ride my bike down the hill" is correct.