user: Question: What's the Proto-Germanic when the Old English is /d/?
Columns: ['Proto-Germanic', 'West Germanic', 'Old English', 'German', 'Dutch']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['*þ', '*[þ]', '[θ]', '/d/', '/d/']
SQL:

assistant: SELECT "Proto-Germanic" FROM "Table" WHERE "Old English" = '/d/';