Final answer:
Flip two letters in 'earth' to create 'hearth', the name for a fireplace, which is the answer to the riddle.
Step-by-step explanation:
The riddle posed in the question is asking which word can be created by flipping two letters in the name of a layer of planet Earth to form the name of a fireplace. The answer to this riddle is hearth, which is obtained by flipping the letters 'e' and 'a' in 'earth'. Thus, the correct answer is option (a) Hearth.
It's a play on words involving a form of anagram — a word or phrase formed by rearranging the letters of another word or phrase. The Earth and hearth are related in this context through the clever rearrangement of letters.
The layer of planet Earth that flips 2 letters to frame a fireplace is the Earth's crust. The Earth's crust is the outermost layer of the Earth and is composed of solid rocks and minerals. It is the thinnest layer of the Earth, ranging from about 5 to 70 kilometers in thickness.