Due to too few sales, it is difficult to recover the research and development and production costs of drugs, so pharmaceutical companies that produce drugs to treat rare diseases will suffer economic losses. The one thing that can most weaken the above conclusion? ['Some drugs for rare diseases also have good effects on other diseases.', 'R & D of drugs to treat rare diseases will promote medical advances.', 'Relative economic benefits, some pharmaceutical factories pay more attention to social benefits.', 'The larger the quantity of medicine produced, the smaller the average cost of medicine per unit.']