Put-Call parity for European options on stock index under BSM model can be used to: show how far in-the-money put options can get. find how far in-the-money call options can get. show the precise relationship between put and call prices given unequal exercise prices and equal expiration dates. that the value of a call option is always twice that of a put given equal exercise prices and equal expiration dates. find the value of a risk-free bond if the prices of call and put options with the same T and K as for put is given from BSM model. O