Q. The concept of 'survival of the fittest' was 1st advocated by

Explanation by: Official MCQ Buddy

The phrase "survival of the fittest" was first coined by Herbert Spencer, a philosopher and sociologist, after reading Charles Darwin's work on evolution. Spencer used this phrase in his book "Principles of Biology" (1864) to describe natural selection.
However, Charles Darwin (A) later adopted the term in later editions of his book "On the Origin of Species", as it aligned with his concept of natural selection.
(C) Haeckel – Known for his work in embryology and ecology, but not related to this concept.
(D) Oparin – Known for theories on the origin of life, not evolution.
Thus, Herbert Spencer (B) is the correct answer.