SORU: boşluğa uygun düşen cümleyi bulunuz
Suddenly the man heard the low hum of an engine. At first he thought that it must be a car travelling along the road he had recently left. ……… . Instead, it grew louder and louder and seemed to be coming from above. He looked up quickly and saw an aeroplane cutting a crazy, zig-zag path across the sky.