Which statement is true for both incomplete and complete digestive systems?
digestion begins outside the cells.
continuous feeding is possible.
the digestive cavity is like a tube.
materials enter and exit through the same opening

Digestion begins outside the cells.

Explanation:

Digestion is split into two types -- extracellular and intracellular.

Extracellular digestion -- the cells are secreting an enzyme that is helpful in digesting, but only outside the cell.

Intracellular digestion -- breaking down of food molecules is occurring inside of the cell.

Digestive system is also split in two categories:

a. Complete

b. Incomplete