the one that would be considered the highest risk portofolio would be : a portfolio made up of 60% stocks, 30% mutual funds, and 10% Treasury bonds.
Stocks is considered a high risk investment because it is very hard to predict the market and you could potentially lose a huge amount of your investment in a really short time.
As for mutual fund, it's considered a high risk because you basically handed over your investment to a third party and you won't be having any control on how it would be used.