Answer: Protoxylem.
- A Protoxylem
- B Metaxylem
- C Secondary xylem
- D Heartwood
Correct answer: A. Protoxylem
Explanation: Protoxylem is the first primary xylem to mature, with narrow elements; the later, wider metaxylem follows.
Concept context
Internal tissue organisation: meristems, permanent tissues (xylem, phloem, parenchyma), and secondary growth. Frequently tested in NEET.