Suppose the risk-free interest rate in the market is 2% p.a. and a unit of a non-dividend paying stock currently costs £24 . which of the following options expiring in one year create arbitrage opportunities? select one or more:

a. an american put option with strike 25 and current price 0.97
b. a european call with strike price 25 and current price 1.34
c. a european put option with strike 23 and current price 1.23
d. a european call with strike price 23 and current price 1.23