Chemistry
The two metal ions that cause hardness to water are:

Calcium, Magnesium
Sodium, Magnesium
Sodium, Potassium
Sodium, Calcium

ANSWER DOWNLOAD EXAMIANS APP

Chemistry
A solution is

A solid dissolved i water
A homogeneous mixture of two or more substances
A solid dissolved in a liquid
A mixture of two liquids

ANSWER DOWNLOAD EXAMIANS APP