Standard tissue layers in a dicot stem cross-section

Steps:

• Locate tissue 1 as the broad ground tissue layer just inside the epidermis: identifies as cortex.
• Identify tissue 2 as the single inner layer bounding the cortex: confirms endodermis.
• Recognize tissue 3 as the outer part of vascular bundles with sieve elements: designates phloem.

Why A is correct:

• In dicot stems, cortex occupies the region between epidermis and endodermis for storage and support, endodermis regulates water flow via Casparian strip, and phloem lies external to xylem for sugar transport.

Why the others are wrong:

• B misplaces endodermis outward (it's inner cortex) and confuses epidermis (outermost) with internal layers; xylem is inner to phloem.
• C incorrectly positions endodermis and epidermis; phloem isn't central vascular tissue.
• D wrongly labels outer tissue as pith (central core) and ignores cortex placement.

Final answer: A