Question

What animal has the strongest skin/shell?

Answer 1

Hint: Every organism is provided with an outer covering that encloses all the bodily organs into a single unit. Besides, it also separates the body from the outer environment and thus plays a crucial role in providing protection.

Complete answer:
There are many shell bearing organisms on the planet amongst which tortoise shells are the strongest. Tortoise is known for bearing a heavy and strong shell covering over its body. This shell is always in proportion with the tortoise in terms of weight. This kind of body feature is generally imparted to the organism for providing protection against predators. However, carrying such a heavy weight at the back of the body reduces the tortoise's locomotion speed. Therefore, protection takes speed as a compensation cost.
In a tortoise body, this shell, besides working as a protective layer, also functions as a house such that whenever they predict any kind of unfavourable environment or any other condition they accommodate themselves inside this shell. This shell bears a cavity that is just enough for a tortoise body. Thus, it functions as a spare house for tortoise's as well.
Sometimes for protection reasons, in some organisms skin is replaced by some hard cover which is commonly called shell. In most common cases this shell is made up of calcium carbonate or bicarbonate that imparts its qualities like strength, hardness, etc.

Note:
Rhinoceros are another kind of organisms that are found to have thickest skin which is also the strongest skin cover after the tortoise body. Therefore, it is asked about the strongest body cover irrespective of it being skin or shell then the answer will be Tortoise shell whereas whenever questions specifically asks about strongest skin then answer will be Rhinoceros.