"Which one" means what? Investing Only on one single coins among those, Won't make you billionaire. Rather that was stupid way to loose your whole $40,000.... Think about it, only btc or eth or bnb can't trun your money from 40000 to 1 billion, impossible for each of those to pump hundred times. Rather invest with all of those with fix ratio. All of those are good coins. just make sure, durning investment, you are giving priority to btc eth and bnb with more percentage among those altcoins
Probably even if he invest in altcoins he won't be able to turn 40,000$ into a billion dollars, because that is a really unrealistic goal. Besides the fact the risk to take with altcoins is too high. Personally, I would invest 90% of the funds into BTC and 10% into solid altcoins like ETH. It's a conservative strategy, but reliable on long term to prevent losses and achieve consistent gains. However, each investor has their own strategy and goals, so always make your own research to best fulfill your plans.
normally, with that amount, we would choose a low risk investment, i would also choose bitcoin for that. However, if it is an altcoin, then the choices are Ethereum and BNB. It's just that, realistically, I might prefer investing in bitcoin with a higher percentage than altcoins. In addition, with $ 40k, we should need to divide some of the investment into several parts. it's better than investing everything in one basket.