What scientist do that is the basis for their investigation?

If you eat to much it could kill you.

By water evaporation from the leaves is created a negative pressure at the top of the tree that promotes the ascension  of the water through channels that are called xylem. there are also two molecule forces that are involved: the intra-water molecules cohesion (water molecules stick to each other) and the adhesion when the water molecules stick to the channels they are running in. this is what enables water to go from the roots to the top of a tall tree.

Im not sure if you still need this but the answer is 300 hz450 hz  i just did this lesson so , wish you the best of luck and take care

Your answer is going to be b.