Which best describes the purpose of a controlled experiment?
to make sure the results of the experiment support the hypothesis

a. to prevent a dangerous condition resulting from a reaction

b. to examine whether one variable causes a change in another

c. to prevent an undesired change in a variable

there is no correct list among the choices you've provided.

the list might look something like this:

-- baby human

-- piccolo

-- flute

-- soprano singer

-- trumpet

-- tenor singer

-- trombone

-- baritone singer

-- baritone horn

-- bass singer

-- tuba

since i had to make up the list myself, i made it easy on myself, and i didn't try to shuffle the string instruments and woodwinds into it too.

the displacement produced by the body.  

the amount of force subjected to the body.  

the angle between the direction of force and displacement