In Ca₃(PO₄)_x, the value of x is:

1. 1
2. 2
3. 3
4. 4

In C₂H₄, the valency of carbon is:

1. 2
2. 1
3. 4
4. 3

A chemical equation is always balanced to satisfy the conditions of :

1. Law of constant proportions.

2. Gay Lussac's law

3. Law of conservation of mass

4. Law of mass action.

One "μ" stands for :

1. One atom of any element
2. 1/12th of hydrogen atom
3. An atom of carbon (C-12)
4. 1/12th the mass of carbon atom (C-12).