1. The beak depth of a finch is the distance from the top of the beak to the bottom, as shown.

An atom's smaller negative particles are at a distance from the central positive particles, so the negative particles are easier to move. 

You need to be more specific.  i really don't know what a "motion map" is.you can draw a graph of an object's position, distance, displacement, speed,velocity, or acceleration versus time, or you can draw a graph of the object's x-position versus its y-position and not give any information about time at all.if the graph presents position or displacement against time,  then constant velocity is a straight line . . i.e. a line that has  constant slope.if the graph shows speed against time, then constant velocityis a horizontal piece of line.if the graph shows acceleration against time, then constant  velocity is a piece of line that lies on the x-axis . . it's value is zero. 

Answertechnician (a) is correct;

The answer is periosteum