All life on earth has descended from a common ancestor this theory was accepted when

a. a majority of scientists agreed with it

b. different scientists expressed different views on it.

c. newspapers and science magazines published it.

d. several experiments gave non-testable results for it.

A. A majority of scientists agreed with it

Explanation:

The famous theory called the theory of common descent, states that all the living organisms of the earth have arisen from a common ancestor. This notion was first proposed by a French mathematician,Louis Maupertuis duirng 1740s who was of the view that all organisms had a single ancestor and evolutionary process with the passage of time resulted in the specie diversification.

After that, in 1790s another philosopher Immanuel Kant, suggested that all organisms seem to have a common ancestor. In the same period of 1790s, another scientist , Erasmus Darwin who was the grandfather of Charles Darwin also suggested that all the organisms might have a single ancestor who went through the process of evolution to bring all the majesty into life.

Charles Darwin was the first scientist who worked on this notion for alot of time and proposed the theory of common descent,in his book, On the Origin of Species.

After it, many scientists got agree with this theory such as,  Vernon Kellogg in 1907 and T. Ryan Gregory in 2008 and many others explain that no reliable observations exists which contradicts the theory of common descent.

Therefore, option A is the best option.

Hope it helps!