Answer: 8, which is basic
Explanation: The hydrogen ion concentration is 1.0 x 10^-8 mole per liter. Using [H+] = 1.0 x 10 -(pH) the pH is 8. A pH above 7 is basic.
The answer is Solid.
This is on account of the substances that develop a solid are packed in a settled, firmly pressed geometric plan.
H2O is a compound. So it's second one.