Question

a scientist is comparing the outer structure of an onion cell, structure x, to the outer structure of a human skin cell, structure y. which generalization is true about the types of structures being examined? structure x is not living, and structure y is living. structure x can be found in some human cells, and structure y can be found in some plant cells. structure x is only found in plant cells, and structure y is found in plant and animal cells. structure x is semipermeable, and structure y is selectively permeable.

Explanation:

Onion is a plant, and plant cells have a cell - wall (structure X) which is unique to plant cells. Human skin cells are animal cells, and both plant and animal cells have a cell - membrane (structure Y).

Answer:

Structure X is only found in plant cells, and structure Y is found in plant and animal cells.