Which of the Following Statements Provides the Best Evidence That

Which of the following statements provides the best evidence that there is a common genetic code that demonstrates the unity of life?

A) Bees, birds, and bats all have wings and fly.
B) Bacteria, mushrooms, and cats all have DNA.
C) Many insects can pollinate only a particular species of plant due to many generations of evolutionary adaptation.
D) Through genetic engineering, a gene from a firefly can be inserted into a bacterium to make it glow.