Final answer:
The correct option is 'She fell off the cycle.'
Step-by-step explanation:
The correct option to complete the sentence would be She fell off the cycle. 'Off' indicates the movement away from the cycle. It is important to use the correct preposition to convey the intended meaning. In this context, 'over' and 'onto' are not appropriate as they suggest a different type of movement. 'Beside' means being at the side of something, and 'under' means being beneath something.
Learn more about prepositions