Diffusion

Answer: C

High → low = diffusion.

Trap A Mixes up a pair of similar technical terms: Make a two-column table for each confusable pair with one defining feature each, and a memory hook (aTLas holds the 'world' (skull) and nods; aXis lets you shake 'no'). Underline the defining feature the stem gives before you look at the options.

Trap B Reverses a direction, order or effect: Before answering, say the process out loud in order with arrows (receptor → sensory → relay → motor → effector; lungs → pulmonary vein → left atrium). Then ask: does my option point the same way? If an option is the mirror image of a fact you know, it is a trap.

Trap D Plant transport misconceptions: Xylem: water and mineral salts upwards (dead, lignified vessels). Phloem: manufactured food (sucrose) both ways (translocation). Transpiration rises with heat, wind, low humidity and light; falls in humid, still air.