Q: Four thermal heaters A,B, C and D are used in the R & D department of Raliance chemicals Ltd. Only one heater can be used on any day . If heater A is used on any day, neither A nor C can be used the next day. If heater C is used on any day, neither C nor D can be used on the next day. If heater C is used on any day, then A has to be used the next day. If heater D is used on any day, then B has to be used the next day. If heater D is used on the third day and different heaters are used on first and fourth day, which heater is used on the first day ?    (1) D       (2) A       (3) B        (4) C