Answer:
(4) Some studies suggest that texting doubles a driver’s reaction time to roadway hazards.
Explanation:
Sentence (4) states that some studies have suggested that if drivers text during driving, their reaction time to roadways hazards doubles as compared to when they don't text during driving.
Sentence 1, and 2 do not say anything about texting.
Sentence 3 although talks about text conversation as a common distraction, but it does not suggest impairing the drivers as strongly as it does in sentence (4) i.e doubling the response time.
