A) NO...3 months is conclusive (and you've been told this)
B) ppl with SEVERELY compromised immune systems might need to test out to 6 months. this would be ppl who are on anti-rejection drugs after an organ transplant...ppl on chemotherapy...or chronic, long term iv drug abusers.
C) cant answer that one. it could be outdated material...not educated...who knows?? the CURRENT guideline is 3 months.