thomas peterffy is the chairman of interactive brokers.are watching some options expiration today. markets are weak, maybe a four-week low or the s&p 500, if we stay here. stay with us. us. amanda: this is bloomberg markets. i'm amanda lang. alongside matt miller. it is time for stock of the hour. a series of options expiration's. we are seeing weakness and close to a four-week low, but just about 1% this week, as we head into these options expiration's. stocks editor dave wilson is here. september is typically a week month. what is going on? dave: historically, the s&p 500 has done the worst in september out of all the months in the year. what we have going on today is what we call triple witching. it used to be quadruple witching. he will get into the difference. we are talking about the expiration of stocks index futures, index options, and options on individual shares. it used to be single stock futures, but they no longer trade. on days like today, you get a burst of trading at the open, another burst at the close. the numbers that ar

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