Answer: B : collect water
The excretory system is the system of organism's body that performs various functions to expel out waste products like salts, nitrogenous wastes like ammonia and excess of water. There are several parts which are involved in the process of excretion these includes sweat glands, liver, kidney system and lungs. In a typical excretory system such as kidney a filtration process occurs where unwanted salts like ammonia and excess water are filtered out, out of this waste certain amount of necessary products are selectively reabsorbed in the kidney.
On the basis of the above description, collection of water is not the function of the excretory system.