Now build a model of salt. Place your materials on a sheet of paper. The regular-size marshmallows can represent the larger chlorine atoms, and the mini marshmallows can represent the smaller sodium atoms. Connect the marshmallows with toothpicks using the picture as a guide. What was difficult about building the model?

The answer is  a.first and third quarters 

Answertraveling around a circular trackexplanation"traveling around a circular track" is the best answer as you could be traveling around a circular track at a constant speed. your velocity would therefore have the same magnitude but will always be constantly direction. since acceleration is the rate of change of velocity, the rate of change will only involve the direction of velocity and not the magnitude.wrong choices: "an object at rest" does not accelerate at all"increasing speed while traveling around a curve" means that the acceleration will not be constant due to only change in direction; it will be constant due to both magnitude and direction"an object in free fall" does not necessarily change direction 

Maybe because they hurt or you bleed a lot