The correct atomic symbols for carbon, calcium, copper and cadmium respectively are:

1. Ca, C, Cu, Cd
2. Ca, C, CO, Cd
3. C, Ca, Cu, Cd
4. Ca, Cl, Co, Cd

Hydrargyrum is the Latin name of:

1. Gold
2. Silver
3. Mercury
4. Platinum

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