Solution: 2 Marks
The International System of Units, universally known as the SI (from the French Systeme International d'Unites ) is necessary because lack of the standard unit of measurement would cause confusion and a waste of time in converting from one unit to another all the time.

Multiple Motions: 1 Mark
Explanation with example: 2 Marks
When a body possesses more than one simple motion, it is said to have multiple motions.
Example: You are traveling in a  train. Wheels of a train has both rotational and translational motion. Thus they have 2 kinds of motion, i. e. multiple motions.

Each Point: 1 Mark
1) Rectilinear motion         

2) Circular motion         

3) Rectilinear motion

Significance of measurement: 2 Marks
Examples: 1 Mark
Measurement helps us to compare unknown quantities with the known quantities. Measurement helps us make quantitative statements about how big, how long, how fast things are. Without measurement, the final product will be full of errors. Examples:- Speedometer is used to measure the speed of the vehicles. The measuring tape is used to measure the length of anything.

Solution: 2 Marks
The size of the foot varies from person to person. If footsteps of two persons are used to measure the length respectively, then the two distances may not be equal. Thus, a footstep is not a constant quantity. Hence, it cannot be used as a standard unit of length.

For each step: 1 Mark
Following are the steps to measure the length of a curved line:

1) First of all, we have to take a thread.

2) Now place the thread along the path of the curved surface.

3) Mark the thread at the endpoint up to which you want to measure the length.

4) Place the thread on the scale starting from zero to the marked endpoint.

5) Measure this length with the help of the scale.

Similarities: 2 Marks
Differences: 3 Marks
Similarities

1) Both are undergoing rotational motion.

2) The distance of any point on the wheel or ceiling fan from the center of wheel or ceiling fan respectively will remain constant.

Differences

1) The ceiling fan is doing only rotational motion, whereas wheel is doing the translational and rotational motion.

2) The position of the center of ceiling fan does not change, whereas the position of the center of wheel changes after motion.

3) The ceiling fan is doing only one type of motion, whereas wheel is doing multiple motions at the same time.

Different modes: 2 Marks
Example for different modes: 1 Mark each
Transport modes are the means by which people and freight achieve mobility. They fall into one of three basic types, depending on over what surface they travel – land, water, and air.
Land: train, bus, and car.
Air: Aeroplanes, Spacecraft, and Gliders.
Water: Ships, Boats.

Modes of transport are means by which we can move people or objects from one place to another. Various modes of transport are land, air, water. We can also use engine powered vehicles such as cars, ships, trains as a mode of transport.
A chair is not a mode of transport. We use it to sit on it and rest.