Features of Phloem Sieve Tube Elements Steps:

• Identify sieve tube elements as living, enucleate cells in phloem for sugar transport with thin walls.
• Confirm presence of cytoplasm for facilitating mass flow of sap.
• Note absence of lignified walls, mitochondria, and typical plasmodesmata; they lose most organelles.
• Recognize pits in sieve plates as specialized structures allowing sap passage between elements.

Why C is correct:

• Sieve tube elements contain cytoplasm for transport and pits in sieve plates, per definitions of phloem structure in plant physiology.

Why the others are wrong:

• A includes lignified walls, characteristic of xylem not phloem.
• B includes lignified walls and mitochondria, both absent in mature sieve tubes.
• D omits pits, essential for connectivity in sieve plates.

Final answer: C