What is meant by physical balance?

Ineed the answer to question 1 , i’m desperate

Awater-filled u-tube manometer is used to measure the pressure inside a tank that contains air. the water level in the u-tube on the side that connects to the tank is 5 ft above the base of the tank. the water level in the other side of the u-tube (which is open to the atmosphere) is 2 ft above the base. determine the pressure within the tank.

Which of the following is not a transverse wave? a) soundb) lightc) radiod) all of thesee) none of these