ANS:D - liquid ammonia.

Liquid ammonia, often simply referred to as "ammonia," is an inorganic compound with the chemical formula NH3. It is a colorless gas at room temperature but can be easily liquefied under moderate pressure. Here are some key points about liquid ammonia:

1. Physical Properties: At room temperature and atmospheric pressure, ammonia exists as a gas. However, when cooled to temperatures below its boiling point of -33.34°C (-28.12°F) and compressed, it can be liquefied to form liquid ammonia. Liquid ammonia is clear and colorless with a pungent odor.
2. Use as a Fertilizer: Liquid ammonia is widely used in agriculture as a source of nitrogen fertilizer. It contains about 82% nitrogen by weight, making it one of the most nitrogen-rich fertilizers available. When applied to soil, liquid ammonia undergoes hydrolysis, releasing ammonium ions (NH4⁺) which are then converted into plant-available nitrate ions (NO3⁻) through microbial processes.
3. Industrial Applications: Liquid ammonia has numerous industrial applications. It is used as a precursor for the production of various nitrogen-containing compounds, including ammonium salts, nitric acid, and urea. It is also used in refrigeration systems as a refrigerant due to its low boiling point and heat-absorbing properties.
4. Household Uses: Ammonia solutions are commonly used as household cleaners due to their ability to dissolve grease, grime, and stains. Dilute ammonia solutions are effective for cleaning surfaces, floors, and windows. However, it is important to use ammonia solutions with caution and proper ventilation due to their strong odor and potential irritant properties.
5. Safety Considerations: Liquid ammonia is highly reactive and can cause burns upon contact with skin or eyes. It is also toxic if inhaled in high concentrations. Proper handling procedures, including the use of personal protective equipment and adequate ventilation, are essential when working with liquid ammonia.