Final answer:
The correct processes required for long-distance transport in phloem are active transport through parenchyma cells and cohesion between water molecules. Therefore, the answer is b. II and III only.
Step-by-step explanation:
The long-distance transport in plants through the phloem involves complex interactions between several processes. To achieve this movement, there is a reliance on negative water potential, which is essential for drawing water into the root hairs. Active transport is also a critical process, occurring through parenchyma cells and companion cells to load sucrose into the phloem, creating a water potential gradient that draws water into the sieve tubes. Cohesion between water molecules is crucial for maintaining the integrity of the water column as it moves through the plant. Contrary to one of the options given, evaporation or transpiration primarily occurs as part of the water transport through the xylem, and while it helps maintain a water potential gradient, it is not a direct driver in the phloem transport process.
The correct option that includes the necessary components for phloem transport is b. II and III only, which are active transport through parenchyma cells and cohesion between water molecules. Option I, a positive water potential, is in fact the opposite of what is needed since the process relies on negative water potential. Option IV, evaporation of water molecules, relates to transpiration's role in xylem transport rather than phloem transport.