Which of the following can be used as directional control valves?

A) check
B) pilot
C) spool
D) all of the above

Directional Control

The mechanism or system used to steer or change the direction of a vehicle or a machine part.

Pilot

Any of a number of devices that receives a signal and then effects an action; can also be known as a relay.

Spool

A cylindrical device around which materials such as thread, wire, or film are wound for storage.