Everyday Science

The ionosphere contains charged particles that reflect and refract radio waves, enabling long-distance radio transmission. Other layers like the troposphere, mesosphere, and stratosphere do not have this property.

Mercury is the closest planet to the Sun, so it has the highest orbital speed according to Kepler's laws of planetary motion. Therefore, Mercury moves around the Sun faster than any other planet.

Wind speeds of 10–13 kph (kilometers per hour) are generally light breezes that cause minor or no damage. Considerable, severe, or extreme damage typically occurs at much higher wind speeds.

The four fundamental states of matter are solid, liquid, gas, and plasma. Plasma is considered the fourth state of matter because it consists of ionized gas with free electrons and ions, distinct from the other three states.

Venus is the brightest planet visible from Earth and is easily seen with the naked eye, often called the 'Evening Star' or 'Morning Star'. It is more visible than Mercury, Mars, or Jupiter under normal conditions.

The term 'toy age' typically refers to early childhood, the period when children begin to play with toys and develop motor and cognitive skills. It does not encompass late childhood or babyhood entirely, so 'Early childhood' is the most accurate choice.

An anemometer is the instrument specifically designed to measure wind speed, whereas a barometer measures atmospheric pressure, a hydrometer measures liquid density, and a hygrometer measures humidity.

Basic metals cannot be converted into gold by heating, beating, or chemical reactions. Conversion into gold requires changing the atomic nucleus, which is achieved through artificial nuclear radioactivity (nuclear reactions).

A biosensor is a device that uses biological molecules to detect chemical substances. It is commonly used to measure blood glucose levels, especially in diabetic patients, making option A correct.

Salinity of seawater is conventionally expressed as the amount of dissolved salts, mainly sodium chloride, in grams per kilogram of seawater. This means salinity is measured as grams of salt per 1 kilogram of seawater. Therefore, the correct answer is option C: 1 kg. The original answer 'A' (1 gram) is incorrect because salinity is not measured per gram of seawater but per kilogram.