If a base is added to water, what will occur?
hydronium ion concentration is increased.
hydroxide ion concentration is decreased.
[h+] is decreased.
[oh-] is decreased.

C

Explanation:

The first and most obvious statement is that [OH-] is increased, but that is not offered to you.

The second most obvious statement is that the [H+] ion is decreased. That is offered to you. It is C

[H+] is decreased.

Explanation:

Arrhenius Theory:

An acid is a substance which produces one or more hydrogen ions, (H+) in aqueous solution.

Examples:

A Base is a substance which produces one or more hydroxyl ion or  hydroxide ion (OH-) in aqueous solution.

Examples

Please note:

(aq) stands for aqueous which means in the presence of water that is, water  acts as a solvent

So, on adding a base to the water increase in will take place and this will decrease the Hydrogen ion concentration  

Pure water contains

if the solution is acidic

if the solution is Basic

we can conclude that the melting point of table salt is above room temperature (it's actually 801 deg c). the melting point of mercury must be below room temperature (- 39 deg c).