Suppose you increase your walking speed from 7 m/s to 15 m/s in a period of 3 s. what is your acceleration?

You asked the question twice I answered it on the last one

i am pretty sure it is c because when people are closer together, they cannot move as freely. picture being in a mostly full elevator, for instance. the people are right next to you, and you can barely move.

luster is not a good characteristic to use by itself because luster is the property of minerals that indicates how much the surface of a mineral reflects light. the luster of a mineral is affected by the brilliance of the light used to observe the mineral surface.