Sarah and maria made a telephone using two cans and a string. they pulled the string tight and maria went out into the hallway. when maria spoke into her can, sarah could hear her because the sound waves
a) travelled through a vacuum.
eliminate

b) travelled from the cold hallway to the much warmer classroom.

c) travelled from the vibrating can through the string to the other can.

d) travelled through the air from maria to sarah even though they were in different places.