The correct answer is: A. 7000 km per hour.
A synchronous orbit is an orbit in which an object takes the same amount of time to orbit the Earth as it takes the Earth to rotate on its axis. This means that the object appears to stay in the same position in the sky, relative to the Earth’s surface.
The altitude of a synchronous orbit is 36,000 km. The velocity of an object in a synchronous orbit is about 7000 km per hour.
The other options are incorrect because they are not the velocity of an object in a synchronous orbit.