A standing wave also known as a stationary wave, is a wave in which its peaks or any other point on the wave do not move spatially.

This phenomenon can occur because the medium is moving in the opposite direction to the wave, or it can arise in a stationary medium as a result of interference between two waves traveling in opposite directions. The most common cause of standing waves is the phenomenon of resonance, in which standing waves occur inside a resonator due to interference between waves reflected back and forth at the resonator's resonant frequency.

Hence, standing wave occurs when a wave reflects upon itself.

As per the latest updates, India is :

• Largest producer of milk.

• Largest producer of millets in the world.

• Largest producer of jute.

• Largest producer of ginger.

• Largest producer of bananas.

• Largest producer of castor oil seeds.

• Largest producer of mangoes.

• Largest producer of safflower oil seeds.

• Largest producer of papayas.

• Largest producer of cottonseed (As per International Cotton Advisory Committee (ICAC) report for the month of March 2017)

• Second largest producer of tea, the first position being held by China.

• Second largest producer of sugarcane, the first position being held by Brazil.

• Second largest producer of wheat, the first position being held by China.

• Second largest producer of onions, the first position being held by China.

• Second largest producer of potatoes, the first position being held by China.

• Second largest producer of garlic, the first position being held by China.

• Second largest producer of rice, the first position being held by China.

• Second largest producer of cement., next to China.

• Second largest producer of silk, the first position being held by China.

Domestic policy is an area of public policy which concerns laws, government programs, and administrative decisions which are directly related to all issues and activity within a nation's borders.

It differs from foreign policy, which refers to the ways a government advances its interests in world politics.

Hence, Option A, The Supreme Court strikes down a law that bans importing inefficient automobiles is an example of domestic policy action.

According to 2018 January reports, Mukesh Ambani is the first richest person in India being 18th in the world, followed by Azim Premji and S.P. Hinduja in second and third places.

You have to actually count all the balls in the pyramid.
Simple way is to count the balls in each level.

So lower most level lets say 1st level has 4 x 4 balls; i.e. 16 balls
Similarly 2nd level has 3 x 3 balls; i.e. 9 balls.
3rd level has 2 x 2 balls; i.e. 4 balls.
The top most level has just 1 ball.

So the total number of balls is 16+9+4+1 = 30.

So the image has 30 Balls in all.