Tonitrophobia is the specific phobia referring to an abnormal and persistent fear of thunder. While the question includes '1.' which might suggest it's part of a numbered list, the answer is straightforward - fear of thunder is the correct definition. The term comes from 'tonitru' meaning thunder in Latin. Option A (fear of strangers) is xenophobia, and option B describes onychophobia, though the wording about 'other people's nails' is unusual.