The force applied to the machine to do work is called:
A) Load
B) Effort
C) Efficiency
D) Fulcrum

Hint: Work is nothing but applying force to move an object a distance. When the force and motion are in the same direction. The force applied to the machine to do work is the effort taken to move the machine.

Complete answer:
A machine is a device that helps make work easier to perform by accomplishing one or more of the following functions:
Transferring force from one to another.
Changing the direction of force etc.
There are certain concepts we need to know regarding machines.
1. Load-
Load is the weight that a lifting machine lifts. The load is also a force but it is not the force that we apply to the machine to make it perform some work. The weight that the lever is about to lift is called load.
2. Effort-
For any machine to do some amount of work there is a need of force and some displacement should take place due to that force. This force that is applied or supplied to the machine for the purpose of making the machine do some work is called effort.
3. Efficiency-
It is not necessary that the machine produces work equal to the input. The output of a machine can differ from the input. This is efficiency. A measure of how good the machine is at producing work as output. Mathematically it can be written as the ratio of output by input.
4. Fulcrum-
Fulcrum is a prop or support which is used to lift heavy loads by applying low force. In other words it is a device used to increase the efficiency of the lever or lifting machine.
‘Effort’ is the force applied on a machine to make it work.

Note: A simple machine uses a single applied force to do work against a single load force. Ignoring friction losses, the work done by the applied force. The work input is the work done on a machine. The work input of a machine is equal to the effort force times the distance over which the effort force is exerted.