1. a mechanical wave
a. carries energy from one place to another
b. moves through solids, liquids, and gasses
c. is created when a source of energy creates a vibration
d. all of the above

2. in refraction when a wave travels from one medium to another
a. changes speed
b. stays in step
c. always moves in the same direction
d. travels in the opposite direction

plzzz me !
i understand that it is wrong to give answers but i need them for unit 3 lesson 12 , me graduating rides on this

For #1 it's a and for#2 it's c i am really sure for #1 but not that sure for #2 i would double check though 

Is a  vector quantity  that refers to "the rate at which an object changes its position." imagine a person moving rapidly - one step forward and one step back - always returning to the original starting position. while this might result in a frenzy of activity, it would result in a zero velocity. because the person always returns to the original position, the motion would never result in a change in position. since velocity is defined as the rate at which the position changes, this motion results in zero velocity. if a person in motion wishes to maximize their velocity, then that person must make every effort to maximize the amount that they are displaced from their original position. every step must go into moving that person further from where he or she started. for certain, the person should never change directions and begin to return to the starting position.