0 votes 0 votes Which of above three are valid. I know A3 is valid. thor asked Jan 15, 2017 thor 179 views answer comment Share Follow See 1 comment See all 1 1 comment reply Hradesh patel commented Jan 17, 2017 reply Follow Share Here A1: it is valid only forword but not backword so here bi-conditional is not valid other A2, A3 is valid property. 0 votes 0 votes Please log in or register to add a comment.