The hammering on a train track is often heard twice by workers farther down the track; first as the sound travels through the steel and second as the sound travels through the air. this suggests which graph is true?

Acm ruler with main graduations from 1 to 10 from left to right there are 10 secondary graduations between each of the main graduations there is a line that begins. at the left end of the ruler 10 secondary graduations to the left of the “1 main graduation the right end of the line ends on the eighth secondary graduation to the right of 3 how long is the line