Step 1: Concept
Plant anatomy and structure
Step 2: Meaning
This question tests understanding of plant tissues and their composition.
Step 3: Analysis
Sap wood is living tissue composed of cells that transport water and nutrients. Rhytidome, heartwood, and spring wood are all dead or partially dead tissues in the context of mature trees.
Step 4: Conclusion
Only sap wood contains live cells.
Final Answer: (B)