16.Toll-like receptor (TLR) is an evolutionarily cons served innate immune receptor that recognizes pathogen-associated molecular patters (PAMP3) of pathogens. Regarding TLRs, which descriptions is/are CORRECT? (A) Since the structure of mRNAs of viruses and tammalian cells are the same, there is no TLR that recognizes viral mRNA (B) All of the TLRs are located on the cell surface to serve as a frontline defense against pathogens (C) TLR2 recognizes flagellin, a structural protein of flagella of bacteria (D) TLR4 recognizes lipopolysacch charides of g gram-negative bacteria (E)TLR9 recognizes dsDNA of viruses or bacteria