The correct answer is: "Honolulu is the only city that has passed a law to prevent injuries from distracted walking; as a result, smartphone and app makers are trying to create systems to help pedestrians navigate streets while using their smartphones"
The main idea of the article is related to the efforts residents of Honolulu are making in order to adapt in the best way possible to the new regulation imposed by the State Government.
The chosen statement clearly mentions the event that produced the issue which is assessed by the article, which is the new law. Afterward, it effectively summarizes the efforts Hawaiian residents are doing as a response to this event.