Pain is more defined as a symptom
They are useful because of the way they process and digest food. They apply their enzymes externally and then absorb smaller mollecules. This process releases things like CO2 or creates alcohols, and this has historically been used in making drinks like beer or foods like bread and cheese.
C. employment and unemployment
because it is the only one that makes sense
B. xylem and phloem. they transport water and nutrients throughout the plant
3) C. Stomata, as I explained in my previous answer.
4) B. Nonvascular, low-hanging plants living in moist environs don't have to fight gravity nearly as much as tall ones do. So they needn't highly developed vessels to transport to their tips
5) B. Gravity, see above. The higher trees/plants grew, the further their apical structures were from ground water sources, so the lignin-supported, strong vascular tissue (phloem) allows the transport of water against gravity, using a capillary method (benefiting from the adhesive effect of water molecules).
