What does the B cell do that makes it so important?

Here, you go:

Generation of B Cells. The immune system is remarkable for its ability to respond to a great many antigens.

Explanation:

These cells make antibodies which defends and fights out viruses in our bodies.

~Hope This Helps~

you didn't give any options but heres what i can tell you: an inference is likely to change based on additional observations. the latter is something that you have seen or sensed using your sensory organs while the former is like a conclusion out from what you have observed.