Read the following passage and choose the best answer for each blank
An accident between a car and a horse-drawn carriage turned on a green light in the mind of one witness to it. Why not, thought Garrett A Morgan, design a signal that would (1) …… the movement of road traffic? (2) …… a result, in February 1927 Morgan produced the world’s first automatic electric traffic signal.
His invention (3) …… of a pole with two arms that turned round to (4) …… when traffic should move. The words ’stop’ and ’go’ were on different sides of the arms, which automatically turned and (5) …… the right line of traffic when necessary.
Trả lời câu hỏi dưới đây:
(4)