Using Archimedes principle one can find out.

The correct option is B

relative density of a substance

1. The relative density of a substance may be defined as the ratio of the weight of the sample of the substance to the apparent loss in weight of the sample in water.
2. When a body is immersed in water, it displaces its own volume of water.
3. According to Archimedes' principle, upthrust on the body is equal to the weight of this displaced volume of water, which is also equal to the loss of weight of the body.
4. Hence weight of the equal volume of water can be replaced by upthrust or loss of weight in water.
   $R.D.=weightofthesubs\tan ceinair/lossofweightinwater$

Hence, option B is correct.