All living organisms are linked to one another because

(a) They have common genetic material of the same type
(b) They share common genetic material but to varying degrees
(c) All have common cellular organization
(d) All of above

ANS  (b) They share common genetic material but to varying degrees 

In fact, the whole theory of evolution is based on similarity of genetic materials which indicates towards common ancestry for living organisms. Variations in similarity of genetic material give biodiversity which we see all around us.