1) which situation could be represented with a linear graph? a) the speed of a rock rolling down a mountain. b) a snail moving at 10 centimeters every 10 minutes. c) a car accelerating 25 mph until the car reaches 75 mph. d) the speed of a plane as it flies from new york to california.

B is the only answer that could be expressed in a linear fashion. Because when then snail moves 10 centimeters every 10 minutes, that means the snail moves at 1 centimeter/minute. This is linear.
 
We can look at the other problems and see how they are wrong:

A) the speed of a rock would change because it would hit things and decelerate and also accelerate when it starts to tumble faster.
 
C) The answer says accelerating in the statement, so we essentially know instantly that this is wrong because the car isn't traveling at a uniform rate.
 
D) The speed of a plane changes as much as a car because there are restrictions to how fast the pilots can fly at certain altitudes, which would indicate the plane is decelerating and accelerating a lot.
 
Hope this helps!

A) it is created from magma