100 POINTS PLEASE HELP !!! SHOW WORK PLEASE!

Which of the following are properties of mechanical waves? check all that apply ⭕️ particles of the medium move back and fourth, but do not move with the wave. ⭕️ the particles of the medium always move parallel to the wave motion. ⭕️ wave motion begins with a disturbance in the medium. ⭕️ waves transport energy from a source outward, away from the source.

If angle "a" is 25°, angle "b" is: a) equal to angle c b) less than angle c c) greater than angle c

Achlorine atom has 17 protons and 18 neutrons. what is its mass number? what is its atomic number?