You select every tenth student on an alphabetical list of the students in your school. You survey the selected students in their first-period classes. Is this question bias?

Abird on top of a 200 ft bridge tower sees a man standing on the lower part of the bridge (which is 50 ft above the ground). the angle of depression from the bird is 26 ̊. how far is the man from the base of the bridge tower? with explanation and pictures .