$A$ mature sieve tube differs from a vessel in:

Which living cell of the phloem tissue contains a functional nucleus and cytoplasm?

What is the thickening material present in this tissue?

Aerenchyma is found in

Given below are two statements:
Statement $I$: Parenchyma is living but collenchyma is dead tissue.
Statement $II$: Gymnosperms lack xylem vessels but presence of xylem vessels is the characteristic of angiosperms.
In the light of the above statements,choose the correct answer from the options given below:

Where are xylem fibers found?