Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
|  | simple machine |  | purpose |  | example of simple machine |
| --- | --- | --- | --- | --- | --- |
| A(n) | lever | is used to | move a heavy object with little force | for example, in a(n) | seesaw; scissors; crowbar; wheelbarrow; nutcracker; bottle opener; tweezers; human jaw |
| A(n) | wheel and axle | is used to | move a heavy object with little force; move vehicles | for example, in a(n) | skateboard wheels; car wheels; bicycle wheels; cart wheels |
| A(n) | pulley | is used to | move heavy objects up or down a rope with little force | for example, in a(n) | belt sander; bandsaw; tractor |
| A(n) | inclined plane; ramp | is used to | raise or lower a load with little force | for example, in a(n) | wheelchair ramp; loading ramp; funicular railroad; pedestrian ramp; skateboard ramp; half pipe |
| A(n) | wedge | is used to | raise or lower a load with little force; hold an object in place; separate two pieces of an object | for example, in a(n) | hammer claw |
| A(n) | screw | is used to | convert rotational motion to linear motion | for example, in a(n) | corkscrew; bottle top; screw; nut and bolt; |
Question:
What is the main purpose of a pully? Select the correct choice to answer the question or fill in the blank.
Choices:
(A) for leverage
(B) to help a tractor move
(C) to move things with little force
(D) convert rotational force to linear force
Answer:
(B) to help a tractor move