Not a lot. All of them.
The only secure place to put cryptos is a hardware wallet.
The very idea of investing them for benefits is strange. If this type of investing was a normal, legitimate business, why isn't it possible to do it with conventional, government issued money? Why aren't there options to invest regular dollars, and get 40+ % returns yearly? The best possible return would be around 10%, and even that would be risky.
Yet criptos offer you much, much more. BitConnect offers ~1% daily. If you withdraw everything that's 350% yearly. If you reinvest, the yearly compound interest is a freaking 3300%!!!
There's no such thing as free lunch!