Everyday Science

The ionosphere is the layer of the atmosphere that reflects radio waves back to the Earth's surface, enabling long-distance radio communication. Other layers like the troposphere, stratosphere, and ozone layer do not have this property.

Wooden doors absorb water during the rainy season through imbibition, causing the wood to swell and making the doors difficult to open or close.

The scientific study of fingerprints is called dactylography. The other options refer to different fields: dactylology is sign language study, dactyliology is not a recognized term, and dialectology is the study of dialects.

The scientific study of caves is called Speleology. The other options refer to different fields: Haematology is the study of blood, Oology is the study of eggs, and Oneriology is the study of dreams.

A lactometer is an instrument used to measure the purity or specific gravity of milk, which helps determine if it has been diluted with water.

The chemical symbol for water is H2O, which represents two hydrogen atoms bonded to one oxygen atom. The other options represent different substances: O2 is oxygen gas, CO2 is carbon dioxide, and NaCl is table salt.

Nitrogen makes up about 78% of the Earth's atmosphere, making it the most abundant gas. Oxygen is the second most abundant, while carbon dioxide and hydrogen are present in much smaller amounts.

Pedology is the scientific study of soils, including their formation, classification, and mapping. The term comes from the Greek word 'pedon' meaning soil.

Wind energy is generated due to the uneven heating of the Earth's surface by the sun, which causes air movement. This movement of air, or wind, is harnessed to produce energy.

The largest type of shark is actually the Whale Shark, which is not listed among the options. Of the options provided, the Great White Shark is the largest, but it is not the largest shark overall.

Jupiter is the largest planet in the solar system by both diameter and mass, making it the correct answer.