1. Which of these statements best describes the Earth’s crust? A. It includes the continents but not the ocean floor.
B. It is a layer of molten rock that moves in circular patterns.
C. It is a system of large masses called tectonic plates that slowly move together or apart.
D. It is a layer of solid rock that remains the same throughout time.

answer: option (a) is the correct answer.

explanation:

the measurement of hydrogen ions in a solution is known as ph.

if ph of a solution is less than 7 then the solution is acidic. if ph of a solution is greater than 7 then the solution is basic.

when the ph of a solution equals 7, then the solution is considered as neutral.

the ph of pure water is 7, therefore, it means that concentration of hydronium ions equals that of hydroxide ions.