Answer: C. Ordinal
Step-by-step explanation:
Ordinal Data is a statistical method of measurement that is able to categorize variables as well as order them in a certain manner. Ordinal data however is unable to tell the scale of difference in the different variables.
The Investment Firm was able to categorize the different companies and it was as well able to order them with these classifications because as we know, "AA" will be higher than "B".
However we do not know just how different in quality these 2 bonds are because there is no measurement scale.
This is therefore an Ordinal level data.