Answer:
Structure X is only found in plant cells, and structure Y is found in plant and animal cells.
Explanation:
The structure found on the outside of the onion cell is the cell wall, which is specific to plants. The structure found on the outside of the skin cell is the cell membrane, which is found on all cells.
Structure X is not living, and structure Y is living. - this is false, both animal and plant cells are living.
Structure X can be found in some human cells, and structure Y can be found in some plant cells. - this is false, the opposite is true.
Structure X is only found in plant cells, and structure Y is found in plant and animal cells. - this is true structure X is the plant cell wall, and structure Y is the cell membrane
Structure X is semipermeable, and structure Y is selectively permeable. Semi-permeable and selectively permeable are essentially the same thing - it means the barrier allows some substances to pass through but not others.