Movement into and out of cells — practice question

Which statement gives the correct description of an event that occurs during mass flow in phloem sieve tube elements?

• AAny part of a plant where sucrose is loaded into a sieve tube element is called a sink.
• BLoading sucrose into a sieve tube element increases the water potential inside it.
• CMass flow in the phloem is a passive process occurring at the same rate as diffusion.
• DSucrose moves down a hydrostatic pressure gradient in the phloem from source to sink.