The diagram illustrates the loading of sucrose into a sieve tube element. What form of transport is involved in moving the substances in steps 1, 2 and 3?
- A1: active transport; 2: active transport; 3: diffusion
- B1: active transport; 2: facilitated diffusion; 3: diffusion
- C1: facilitated diffusion; 2: active transport; 3: active transport
- D1: facilitated diffusion; 2: facilitated diffusion; 3: active transport