The current knowledge concerning cells is the result of investigations and observations of many scientists. the work of these scientists forms a well-accepted body of knowledge about cells. this body of knowledge is an example of
a. hypothesis
b. controlled experiment
c. theory
d. research plan
and why would be

The correct answer is a. we know this because n (hap) + n (hap) = 2n (dip).

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.