user: Question: What is the average Height when the weight is less than 91 anD the position is D, anD a BirthDate of July 4, 1975?
Columns: ['Position', 'Name', 'Height (cm)', 'Weight (kg)', 'Birthdate', 'Birthplace', '1997–1998 Team']
Types: ['text', 'text', 'real', 'real', 'text', 'text', 'text']
Sample row: ['G', 'Garth Snow', 191.0, 91.0, 'July 28, 1969', 'Wrentham, Massachusetts', 'Vancouver Canucks']
SQL:

assistant: SELECT AVG("Height (cm)") FROM "Table" WHERE "Weight (kg)" < 91.0 AND "Position" = 'D' AND "Birthdate" = 'July 4, 1975';