Elon Musk continues to keep the environmental pressure on bitcoin mining.In response to a tweet saying bitcoin is "greener" than critics say, Elon Musk chimes responds: "Based on what data?"The original tweet by Bitcoin Magazine quoted Kraken CEO Jesse Powell as saying, "I think Elon has some more studying to do."Recall that earlier this week Musk said Tesla would resume accepting bitcoin once he's got confirmation of "reasonable clean energy usage" by miners with a "positive future trend."Meanwhile, Bitcoin rises 0.1% in the last 24 hours to ~$39.1K. Tesla (TSLA) -0.6% in premarket trading.As for bitcoin-related stocks: Coinbase (COIN) rises 0.2% in premarket trading; MicroStrategy (MSTR) rises 0.4%; Riot Blockchain (RIOT) +0.9%; Marathon Digital (MARA) +0.7%; Bit Digital (BTBT) -0.1%; Silvergate Capital (SI) +0.9%.As for other cryptocurrencies: Ether (ETH-USD) -1.3% to $2,430.69; Binance Coin (BNB-USD) +1.6% to $358.68; Cardano (ADA-USD) -0.1% to $1.52; dogecoin (DOGE-USD) -0.1% to 31 cents.