Summarization：the paragraph is followed by an incomplete phrase or sentence which summarizes the main idea of the paragraph. Spell out the missing letter of the word on your answer sheet.

In the movie, the principal character, Leonard, can remember everything that happened before his head injury on the night his wife was attacked, but anyone he meets or anything he has done since that fateful night simply vanishes. He has lost the ability to convert short-term memory into long-term memory.
Leonard’s head injury has r   in his loss of long-term memory.