[" 13.The correct order of decreasing acid strength of "],[" trichloraacetic acid (A),trifluoroacetic acid (B),acetic "],[" acid (C) and formic acid (D) is: "],[[" (1) "A>B>C>D," (2) "A>C>B>D],[" (3) "B>A>D>C," (4) "B>D>C>A]]