Which alloy is used to prepare scientific balance?

Which among the following alloys contains mercury as one of its constituents?

Which metal oxide dissolves in water to form an alkali?

Name the metal which:
$(a)$ becomes blackish after a certain time.
$(b)$ develops a green coating on exposure to air.
$(c)$ does not corrode at all.
$(d)$ is used in making steel.
$(e)$ is non-lustrous.

Which element forms the basis of components like vitamins,proteins,and carbohydrates?

Why is sodium chloride soluble in water but not soluble in kerosene?