The rate of change of displacement of a body with respect to its surrounding, is known

ANS:C - speed

Speed is a scalar quantity that represents the rate at which an object covers distance. It is defined as the magnitude of the velocity vector, without regard to direction. In other words, speed tells us how fast an object is moving, but it doesn't specify the direction in which it is moving. Here are a few key points about speed:

1. Scalar Quantity: Unlike velocity, which is a vector quantity and includes both magnitude and direction, speed is a scalar quantity and only represents the magnitude of motion.
2. Instantaneous Speed: The speed of an object at a particular instant in time is called instantaneous speed. It is calculated by measuring the distance traveled by the object in a very small time interval around that instant.
3. Average Speed: Average speed is the total distance traveled by an object divided by the total time taken to cover that distance. It gives an overall measure of how fast the object is moving over a certain period of time.
4. SI Unit: The SI unit of speed is meters per second (m/s). Other common units of speed include kilometers per hour (km/h) and miles per hour (mph), depending on the context.