In the word "rebuilt," re is a) both a morpheme and a phoneme. c) a phoneme, but not a morpheme. b) a morpheme, but not a phoneme. d) neither a morpheme nor a phoneme

B) a morpheme, but not a phoneme.

Explanation:

Morphology studies the smallest components of language and how they relate to structure and meaning (it focuses on forms).

Re is a morpheme, it comes from Latin.  Morphemes can be a single word.

Re, "meaning again" or "backward"

Since morphemes are the smallest units of meaning, the prefix "re"  usually cannot stand alone, it is added to modify a verb like : reshape: reload, reconsider

Attaching a Re to another word , such as by adding the prefix "re-" to a verb " creates a new word : remember , Remembrance.

the 2nd option is the answer

answer; ///he could not explain why the continents drifted;