The correct answer is D.
A manometer is a device used to measure pressure. It consists of a U-shaped tube filled with a liquid, such as mercury or alcohol. The pressure difference between the two arms of the tube is measured by the difference in the height of the liquid in the two arms.
Alcohol is used in manometers because it has several properties that make it ideal for this purpose. First, alcohol has a low vapor pressure. This means that it evaporates slowly, which prevents the meniscus (the curved surface of the liquid) from becoming too unstable. Second, alcohol has a low density. This means that it can be used to measure small pressure differences. Third, alcohol is non-toxic and non-flammable. This makes it safe to use in a variety of applications.
The statement “alcohol provides longer length for a given pressure difference” is incorrect. The length of the liquid column in a manometer is proportional to the pressure difference. Therefore, alcohol does not provide longer length for a given pressure difference.