The correct statement is: Both a euglena and a white blood cell can survive on their own.
Euglena is a single-celled organism that can perform photosynthesis and obtain food on its own, while white blood cells are a type of cell in multicellular organisms (like humans) that serve immune functions. Although white blood cells rely on the body for the environment in which they operate, they can independently carry out their functions. Therefore, both can be considered capable of "surviving" in their respective contexts.