8.18

                        c
                    +-------+---------+
                    |      "0"     exit "2"
                    |    
                c   |   p
            +-------+-------+---------+
            |     fork     "1"     exit "2"
            |   (atexit)
            |           c
            |       +-------+---------+
            |       |      "0"      exit
            |       |    
            |   p   |   p    
     +------+-------+-------+---------+
    main  fork    fork     "1"      exit

2 must be behind 0/1

B & D is impossible.