The answer to this question would be A and B.
Bonds are considered very low risk for the very simple reason that they are backed by the power of the credit of the United States.
So, the only REAL risk for investors is that the United States default on its debts, that is, that they don't pay their debts. This could happen if all foreign owned debts are called in at once.
Bluetooth was invented by Dr. Jaap Haartsen in the 1990s. The purpose it serves is to connect devices to others, such as speakers, computers, printers, remotes, etc. It has impacted societies in many ways these days. One of the most major is wireless communication, which is a great asset, especially while driving.