Solution:(b) The task could have been completed by the rescue team if there had been uninterrupted power supply. (Correct)(a) The task can have completed by the rescue team if there was uninterrupted power supply. (Incorrect Helping Verbs)
(c) The task could be completed by the rescue team if there was uninterrupted power supply. (Incorrect Helping Verbs)
(d) The task could have to be completed by the rescue team if there was uninterrupted power supply. (Incorrect Helping Verbs)