Answer:
I need more info? Is this a question or a true or false thing?
Explanation:
They may have ran out of oxygen, or they may not have been water dwelling snails, as not all are, lack of food, no flow of water into and out of the tank would cause them to run out of oxygen.
Surface tension is the property that allows bugs to walk on aater
Unicellular organisms are devoid of circulatory systems and will be found living in moist or watery environments to facilitate uptake of nutrients and gases and expulsion of waste by the process of diffusion.
Their cell is structured such that it can engage in direct exchange of substances with its environment. Water serves as the perfect medium or environment through which this exchange can occur.
Gases and nutrients simply diffuse into the cell or are moved into the cell by means of active transport or phagocytosis.
It is oxygen. Hope this helps