ANS:B - 32°

The temperature designation of 32° on the Fahrenheit scale corresponds to the freezing point of water under standard atmospheric pressure. Here's an explanation:

1. Freezing Point of Water: At 32°F (Fahrenheit), water undergoes a phase transition from liquid to solid, forming ice. This means that at this temperature, water molecules slow down and arrange themselves into a crystalline structure, resulting in the solid state we recognize as ice.
2. Historical Context: The choice of 32°F as the freezing point of water on the Fahrenheit scale has historical roots. Daniel Gabriel Fahrenheit, a German-Dutch physicist and engineer, developed the Fahrenheit scale in the early 18th century. He calibrated his thermometer by setting 0°F as the lowest temperature he could achieve with a mixture of ice, water, and ammonium chloride, and 96°F as the average human body temperature. Later, he divided the interval between these two points into 96 equal parts. The freezing point of water was then established as 32°F, which is 32 degrees below the 96°F mark.
3. Common Usage: In everyday life, 32°F is commonly associated with the onset of freezing conditions. It's a crucial reference point for weather forecasts, road conditions, and other situations where the freezing of water plays a significant role.
4. Conversion: In Celsius, the freezing point of water is 0°C. The Fahrenheit and Celsius scales intersect at -40°, so both -40°F and -40°C represent the same temperature. To convert temperatures between Fahrenheit and Celsius, one can use conversion formulas or reference conversion charts.