A. All living species on earth must be taken care of by us.
B. All living species on earth must taken care of by us.
C. All living species on Earth had been taken care of by us.
D. All living species on earth will be taken care of by us.
The given sentence contains one of Model verb (Model Verb = will, shall, can, may, might, could, might, must, would). It is in active voice.
Rule :
Subject + Model verb + be + V3 + Optional Objects.
