Everyday Science

Red, blue, and yellow are the traditional primary colors in the subtractive color model used in art and everyday science. Green is a secondary color made by mixing blue and yellow, so it is not a primary color.

Soil acidity is commonly corrected by liming, which involves adding lime (calcium carbonate) to neutralize acidic soils and increase pH levels. This method is widely used in agriculture to improve soil quality.

Mass is the quantity of matter present in an object, distinguishing it from weight, which depends on gravitational force. Density relates mass to volume, so it is not the direct measure of quantity of matter.

Potassium metabisulphite is commonly used as a preservative in fruit juices to prevent oxidation and microbial growth, thereby extending shelf life. It acts as an antioxidant and antimicrobial agent, making it suitable for preserving fruit juices.

Apples typically contain about 84% water by weight, making option A the correct choice. This high water content contributes to their juiciness and nutritional value.

Eratosthenes was the first known person to accurately measure the Earth's circumference using the angles of shadows in different locations and basic geometry around 240 BCE.

The Sun is the largest natural source of light for Earth, providing the primary illumination and energy. The Moon only reflects the Sun's light, stars are distant and much smaller sources of light from our perspective, and 'None of these' is incorrect.

Radio waves have the lowest energy among the given options because energy of electromagnetic radiation is inversely proportional to its wavelength. Radio waves have the longest wavelength and thus the lowest energy.

The primary function of perspiration (sweating) is to regulate body temperature by cooling the skin as sweat evaporates. While perspiration can help remove some waste, temperature regulation is its main role.

Matter commonly exists in three primary states: solid, liquid, and gas. These are the fundamental states observed under normal conditions. While there are additional states like plasma and Bose-Einstein condensate under extreme conditions, the three states are the most familiar and commonly taught in basic science education.