Open the brackets. Use the Past Simple or the Past Continuous. Mike (park) his bike in the garden when he (see) the sign.

Let's analyze the sentence: "Mike (park) his bike in the garden when he (see) the sign." We need to use either Past Simple or Past Continuous.

The correct form is: Mike parked his bike in the garden when he saw the sign.

Explanation: Both actions (parking and seeing) are completed actions that happened one after the other. Thus, we use Past Simple for both 'park' and 'see'.