#help After taking the contrapositive, what happens if one of the necessary conditions is failed? Does the sufficient condition fail too? For example, /antibodies → /infected or /1wk. What if one is is infected by a virus (infected), does this mean antibodies will be produced?

In other words, if A and B → C. Then /C → /A or /B. What happens to /C if /A fails and becomes A?

How would "silent ←s→ survive" be translated into English since the arrow is bidirectional?