A common hydrometer reads specific gravity of liquids. Compared to the $1.6$ mark of the stem the mark $1.5$ will be
A. upwards
B. downwards
C. in the same place
D. may be upward or downward depending upon the hydrometer

Hint: Working principle of hydrometer is to be used. It is that the floating body displaces a volume of liquid whose weight is equal to its own.

Complete step by step answer:
A hydrometer is an instrument that is used to determine specific gravity.
Specific gravity:- It is the gravity acting on the body with respect to water. It is the ratio of density of objects to the density of water.
Hydrometer operates on the Archimedes principle which states that a solid body displaces its own weight within a liquid in which it floats.
There are two classes of hydrometer –
1. liquids heavier than water
2. liquids lighter than water.
Lesser the specific gravity of any liquid, lighter the liquid will be with respect to water, the deeper the hydrometer will sink. This is because, the greater amount of liquid will be requested to equal the weight of the body.
Hence, $1.5$ mark will be above $1.6$ mark.

So, the correct answer is “Option A”.

Additional Information:
Hydrometers are calibrated for different uses which are given below:
1. For example lactometer for measuring the density (creaminess) of milk.
2. Saccharometer for measuring the density of sugar is a liquid.
3. Alcohol Meter for measuring higher levels of alcohol in spirits.

Note:
In general, one can say that in a hydrometer, higher density mark is downwards while the lower density mark is upwards.The hydrometer sinks deeper in low-density liquids such as kerosene, gasoline and alcohol and less deep in high density liquids such as brine, milk and acids.
A hydrometer analysis is the process in which fine-grained soils, silts and clays and other earth particles are graded.