posted a question
Suppose you own $1 million worth of 30-year Treasury bonds.  Is this asset riskless?  Why or why not?
B.   You own $1 million worth of 90-Day Treasury bills ("T-bills"). You "roll over" this investment every 90 days by reinvesting the proceeds in another issue of 90-day T-bills.    Is this investment riskless - why?  Is it more or less risky than the investment in question A?  
C.  Can you name an asset that is truly riskless?  An asset besides cash?