Answer:
Lichens are not parasitic when they grow on trees, they just use the tree bark as a home. They enrich the soil by trapping water, dust and silt. When lichens die they contribute organic matter to the soil, improving the soil so that other plants can grow there.
B and D. The xylem and the phloem make up the vascular tissue of plants and transport water, sugar, and other important substances around a plant.
The cells that die are emptied, leaving hollow cell walls with their ends open, thus forming pipe-like structures
Hope this helps
C. Ice is less dense than water which means water condenses when it freezes allowing the ice in a lake to float on top of the water preventing the water below from freezing.
C. Positive Feedback
This is because a response to a stimulus( low blood pressure) acts in the same direction as the stimulus ( even lower blood pressure).
This is opposed to negative feedback where the response would go in the operate direction of the stimulus ( I.e. blood pressure increasing in response to low blood pressure)
