Phloem Transport: Sources vs. Sinks Steps:

• Define sources as sites exporting sugars (e.g., mature leaves) and sinks as sites importing for growth or storage.
• Classify root storage organ: imports and stores carbohydrates, functioning as a sink.
• Classify growing leaf bud: requires sugars for cell expansion and development, acting as a sink.
• Classify growing shoot tip: uses imported nutrients for meristematic growth, serving as a sink. Why A is correct:
• A marks all three (root storage organ, growing leaf bud, growing shoot tip) as sinks (✓), matching the definition of sinks as import sites in phloem mass flow. Why the others are wrong:
• B incorrectly marks growing leaf bud as X (not a sink), despite its role in importing sugars for growth.
• C incorrectly marks root storage organ and growing shoot tip as X, ignoring their storage and growth import functions.
• D marks all as X, failing to recognize any as sinks.

Final answer: A