86、He found my father's lost bike by accident 87、When was the car invented? 88、Should these trees often be watered? 89、What invention do you think is the most useful? 90、May I divide these oranges into three groups? 望满意!
87.When was the car invented? 88.These trees should be often watered. 89.What do you think is the most useful invention? 90.May I divide these oranges into three groups?