The image labeled 'A' shows a cross-section of a plant organ. Based on its structure, which appears to be a vascular bundle within a stem or leaf, the tissue labeled 'A' is likely the xylem or phloem, which are the primary vascular tissues responsible for transport.
Without further context or higher resolution, it's difficult to definitively distinguish between xylem and phloem based solely on this diagram. However, if this is a typical representation of a vascular bundle in a stem cross-section, the darker oval structures could represent xylem vessels (responsible for water transport) and the surrounding cells could be phloem (responsible for sugar transport).
Assuming the question refers to the primary transport tissue shown:
Answer: Xylem