A scientist is trying to determine the speed at which an animal can travel by studying the organism’s body. Which combination of systems should the scientist analyze to estimate the speed at which the organism moves? A. muscular and skeletal
B. digestive and excretory
C. nervous and integumentary
D. respiratory and circulatory

I don't know what subject this actually is :)

just go with your heart buddy

not: both offer magnification to the atomic level.

all these collisions do one thing, and that thing is explained in the last option. when dusst, rocks and ice collide, they harden and form giant layers of rocks or hard ice.

d)   to harden materials to form different parts of earth’s layers

hope it ,

bioteacher101

genetic variations are caused by mutations which are random in the population