PH, acids, and bases
One role of the human skin is to help protect the body against bacteria. The optimal pH of human skin is 5.5.
What is true about the pH of human skin?
Choose 1
A
It is basic.
It is acidic.
It is neutral.
0
It is both basic and acidic.

B. It is acidic

Explanation:

Acid refers to the presence of hydrogen ion. If the concentration of hydrogen increases, the solution will be more acidic or if the concentration of hydrogen ions decrease, the solution will be less acidic. There are two methods for finding pH of a solution i. e. pH paper and litmus paper. If the blue litmus turns red, the solution is acidic. The pH ranges from 1 to 6 denotes acid. pH of skin is 5.5 which comes in the above range so it is acidic in nature.

the earth is thought to have been formed about 4.6 billion years ago by collisions from a cloud of hydrogen, helium, rock, ice and other materials. these were pulled together by gravity to form objects in and around earth like- asteroids and small early planets called planetesimals.

so, the best possible answer to this question will be option d- to harden materials to form different parts of earth’s layers