Which letter completes the Russian word «руч…ёк»?

Question

Insert the missing letter and briefly explain the spelling: руч…ёк бежит (“a little stream is flowing”).

Explanation

Ручеёк is formed from ручей. Its spelling retains the combination её: ручеёк.

Ручёк is incorrect in this exercise. The clue “from ручей” helps identify the missing е.