What could not act as a medium for a mechanical wave

Arunner is training for an upcoming marathon by running around a 100-m-diameter circular track at constant speed. let a coordinate system have its origin at the center of the circle with the x-axis pointing east and the y-axis north. the runner starts at (x, y) = (50 m, 0 m) and runs 2.5 times around the track in a clockwise direction.

Select all that applywhat are some basic resources a family is expected to provide for children? educationclothesspending

Estimate of the number of stars in our galaxy