Acceleration means any change in the speed or direction of motion.
Answer:
9.4
Explanation:
magnitude is the sum of the squares.

If you are given horizontal and vertical components, treat those as the rise and run of a triangle, the rise of 8 with a run of 5 and you want to find the hypotenuse.
How do you find the long side of a triangle?
B, since it is the only one that actually conserves matter for certain. In each of the others, matter could still be imbalanced, since for A, for example, it could be 5 Carbons on the right and 5 Chlorines on the left, and that would not balance.