Which one of the following statements about all the four of Spongilla, leech, dophin and penguin is correct ?
A. All are bilaterally symmetrical
B. Penguin is homoiothermic while the remaining three are poikilothermic
C. Leech is a fresh water form while all others are marine
D. Spongilla has special collared cells called choanocytes not found in the remaining three
