1. (20 pts) Multiple choice and fill blank: 1. On A-B PLC, as soon as the instruction "TON" is energized The enable bit the done bit_ the timer timing bit 2. On A-B PLC, on the TON" instruction, when the accumulated Preset The enable bit the done bit the timer timing bit =_ 3. On A-B PLC, when the instruction "CTU" is energized and ACC > PRESET. CU bit = DN bit=CD bit = _, OV bit=_ UN bit = 4. On A-B PLC, when the instruction "CTD" is energized and ACC