A wooden block hinged on post outside a door, is known

The correct answer is (A) Cleat.
Let's break down why:

* A cleat is a small piece of wood, often triangular, that is fixed to a post or wall.
* It acts as a stop or support for something, like a door.
* In this case, the wooden block hinged on a post, serving as an outside door stop, perfectly describes a cleat.

Let's look at why the other options aren't quite right:
* Stop: While a cleat *functions* as a stop, the question asks for the *name* of the wooden block itself.
* Horn: A horn is a projection, but it's not typically associated with a hinged wooden block or door stops.
* None of these: Since Cleat is a valid answer, this isn't correct.

So, the most accurate term for a hinged wooden block acting as a door stop is a Cleat.