Which of the following gas mixtures is used by divers inside the sea?

Holme signal can be given by using which of the following mixtures?

Which of the following is a volatile salt that undergoes sublimation?

Assertion: Diamond is a bad conductor.
Reason: Graphite is a good conductor.

Bleaching powder is obtained by the interaction of chlorine and

$A$ red solid is insoluble in water,but it becomes soluble if a small amount of $KI$ is added to the water. If this red solid is heated in a test tube,it produces a violet-colored vapor and some metallic droplets are observed on the cooler parts of the test tube. This red solid is........