CREATE TABLE table_name_41 (fuel_propulsion VARCHAR(255), year VARCHAR(255), numbers__quantity_ordered_ VARCHAR(255))
For the year 1975, what is Propulsion, with a Number (quantity ordered) of 4756-4788 (33 buses)?
    
SQL: SELECT fuel_propulsion FROM table_name_41 WHERE year = 1975 AND numbers__quantity_ordered_ = "4756-4788 (33 buses)"