A machine is classified as a compound machine if it

A. has moving parts

B. has an IMA greater than 1

C. is made up of two or more simple machines that operate together

D. is very efficient

the answer is very clearly C.

a common example is scissors

The correct option is: A machine is classified as a compound machine if it C. is made up of two or more simple machines that operate together.

Explanation:

Composite machines are mechanical devices that have been formed from two or more simpler machines which are connected in series. In this way, when one of these parts of the composite machine is activated, the rest work in a coordinated manner, being able to offer together a function that individually could not.

Composite machines have operators that work in coordination. These operators can be:

Mechanical operators : They are the elements that allow the operation of the machine turning the force into movement. This set is what is called a mechanism. Energy operators: are responsible for storing energy or force and transform it into another type so that the device can be activated and perform its function.

In short, the correct option is: A machine is classified as a compound machine if it C. is made up of two or more simple machines that operate together.