The correct answer is option B, that is, they require extra attention due to poor reception.
The hands-free devices have an issue, as it can lead to mishaps. When a person tries to focus on more than one activity, the brain may become burdened by the requirement to process information from two or more sources.
Additionally, whenever a person switches between the errands, the brain must devote energy and time redirecting its attention rather than thinking. The more information the brain has to sort at a particular time, the more probability is to suffer from inattention blindness and miss essential clues about the situation of the road.
Thus, to be a safe driver, there is a need to develop mental discipline to remain aimed at a single task as long as the person is driving on the road.