The most authentic exchanges of trading in bitcoin is: Polonix, Coinbase and Bittrex so i personally suggest you to trade in such exchanges ..
My enquiry was not related to trading.
It was so that I can compare the price of XBT-Cboe Bitcoin Futures with the price XBT-Cboe say they are using, which is that on the Gemini Exchange.
And especially those prices on the day that the futures expire.