Directions: The sentence below has one or two blanks, each blank indicating that something has been omitted. Beneath the sentence are five lettered words or set of words. Choose the word or set of words for each blank that best fits the meaning of the sentence as a whole.

Longdale and Stern discovered that mitochondria and chloroplasts __________ a long, identifiable sequence of DNA; such a coincidence could be _______ only by the transfer of DNA between the two systems.