Explanation: Hardware refers to the physical components of a computer system, such as the monitor, keyboard, mouse, and internal components like the motherboard and hard drive. In contrast, software refers to programs and applications, liveware refers to the users operating the computer, and firmware is a type of software embedded in hardware.

Explanation: Wind energy is considered pollution-free because it generates electricity without emitting greenhouse gases or pollutants. It harnesses the power of wind through turbines to produce energy, unlike coal and mineral oil, which release pollutants and carbon emissions when burned.

Explanation: The frequency range of audible waves, which is from 20 Hz to 20,000 Hz (20 kHz), corresponds to the range of sound frequencies that the average human ear can detect. Here’s a brief explanation of this range: 20 Hz (Hertz): This is the lowest frequency that most humans can hear. It is a very low, deep bass sound, like the rumble of thunder or the deep vibrations from a subwoofer. 20,000 Hz (20 kHz): This is the highest frequency that most humans can hear. It is a very high-pitched sound, like a dog whistle or certain high-frequency electronic noises. Frequencies below 20 Hz are called infrasonic and are generally not audible to humans, though they can sometimes be felt as vibrations. Frequencies above 20,000 Hz are called ultrasonic and are also generally inaudible to humans but can be detected by animals and are used in various technologies like ultrasound imaging. The other frequency ranges listed in the options (B, C, D) fall outside the typical range of human hearing.

Explanation: This range encompasses the frequencies of sound that most humans can hear, from low bass tones to high-pitched sounds. Frequencies below 20 Hz are considered infrasonic, and those above 20,000 Hz are ultrasonic, both of which are typically outside the range of human hearing.

Explanation: Riboflavin, or Vitamin B2, is essential for energy production and the metabolism of fats, drugs, and steroids. It also plays a key role in maintaining healthy skin, eyes, and nerve functions.

Explanation: A spectrophotometer measures the absorbance or optical density of bacterial cultures in a liquid medium. As bacteria grow and multiply, they increase the turbidity of the culture, which can be quantified using a spectrophotometer. This allows researchers to estimate bacterial concentration and growth over time.