Questions

Sea appears blue in colour due to the scattering of the rays when they hit water molecules

The correct statement among the given options about the process of scientific inquiry is "It is possible to test hypotheses, such as those involving historical events, without conducting experiments."

Although it is not possible to carry out experiments to test hypotheses about evolutionary relationships between living groups or about the timing of the origin of major evolutionary innovations, such hypotheses can be evaluated by making predictions about the expected findings that would result from these hypotheses. Data can then be collected to test whether these predictions are correct.

Magnesium is dissolved in seawater at a concentration of about 1,000 parts per million and is the only metal directly extracted from seawater.

RADAR - RAdio Detection And Ranging.

A radar system consists of a transmitter producing electromagnetic waves in the radio or microwaves domain, a transmitting antenna, a receiving antenna (often the same antenna is used for transmitting and receiving) and a receiver and processor to determine properties of the objects. 

Radar is an object-detection system that uses radio waves to determine the range, angle, or velocity of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain.

Radio waves from the transmitter reflect off the object and return to the receiver, giving information about the object's location and speed.

Alum is a common alum, potassium aluminum sulphate K2SO4.Al2SO43.24H2O which makes colloidally suspended impurities in water such as clay to settle down.

• Cactus spines are also known as modified bud scales, which are also called modified leaves.

• Cactus spines occur in clusters in the axil of leaves.