Investment grade bonds are rated by which of the following rating agencies?

Investment grade bonds are rated by a variety of established credit rating agencies that provide evaluations of the creditworthiness of issuers and their securities. The most recognized agencies include Standard and Poor's, Fitch, Kroll, and Moody's. These organizations have built a reputation for delivering comprehensive assessments that help investors gauge the relative risk associated with different bonds.

The correct option encompasses these prominent agencies, highlighting that they collectively evaluate investment grade bonds. Investment grade ratings are crucial because they indicate a lower likelihood of default and are thus more appealing to conservative investors seeking to minimize risk.

Fitch, S&P, and Moody's are particularly noteworthy, as they have been industry leaders for many years. Kroll is also impactful, specifically in niche markets, adding value to the investment decisions made by market participants.

Therefore, the inclusion of all these major agencies, effectively establishing a broad consensus on the standards for assessing investment grade bonds, confirms why that option is accurate.