Question

Can someone explain?

Answer 1

Answer: D. Max steered with one hand. While holding his cell phone in the other hand.

A sentence fragment is another term for an incomplete sentence. In option D, the second sentence, 'While holding his cell phone in the other hand', is a fragment.

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All complete sentence must:
1. Contain a subject.
         Ex. He held his cell phone. 
2. Contain a verb.
         Ex. He held his cell phone.
3. Be a complete thought.
        'While holding his cell phone in the other hand' is not a complete thought.
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**Additional information**
'While holding his cell phone in the other hand' is a fragment, but can also be used as an introductory phrase.
        Ex. While holding his cell phone in the other hand, Max steered.

If it is an introductory phrase, it must be elaborated in order to be a complete sentence. You cannot end an introductory phrase with a period.