The atoms of which element will gain electrons to form an ion? oxygen
calcium
lithium
mercury

Explanation:

Oxygen will gain electrons to form ion (O²⁻).

Calcium loses electron to form ion (Ca²⁺)

Lithium loses electron to form ion (Li⁺)

Mercury loses electron to form ion (Hg²⁺)

Here it is stated in question that the element will gain electron it means electron bears negative charge.

Therefore,

Option A is correct ✔.

d.) circle motion requires a force to give it a centripetal acceleration.

c (diamond),

sio2 (quartz)