In the vascular bundles of leaf

• A

  the phloem is adaxial and xylem is abaxial.  

• B

  protoxylem is adaxial and metaxylem is abaxial.    

• C

  metaxylem is adaxial and protoxylem is abaxial.    

• D

  xylem is at the center and phloem is both adaxial and abaxial.