The photomicrograph depicts a vascular bundle taken from a plant stem. Which labels are correct for structures X, Y and Z?
- AX: companion cell, Y: sieve tube element, Z: air space
- BX: sieve tube element, Y: xylem vessel element, Z: air space
- CX: xylem vessel element, Y: companion cell, Z: sieve tube element
- DX: xylem vessel element, Y: sieve tube element, Z: companion cell