The plants growing high in the tree canopy send out roots. the roots are searching for water vapor in the humid air of the forest. this response that aerial plants find water is called
a)germination
b)hydrotropism.
c)phototropism.
d)thigmotropism.

B. Hydrotropism

The response that helps aerial parts of the plant to find water is called as hydrotropism. Tropism refers to the response of the plant growth towards a particular stimuli, such as gravity, sunlight, touch and water. The hydrotropism refers to the growth response of the plant parts towards water. The plant may show positive or negative hydrotropism. A positive hydrotropism refers to the response in which the plant grows towards water whereas the negative hydrotropism refers to a response in which the plant grows away from it.

In the given condition, the plants growing high in the tree canopy send out roots. The roots will absorb the water present in the humid air. Therefore, it is a positive hydrotropism response.

explanation:

for  example, forests have higher evapotranspiration than other ecosystems,  such  as grasslands, because of their deeper roots and greater leaf area. thus forests have a net moistening effect on the atmosphere and become a moisture source for downwind ecosystems.

as the gila monster consumes the eggs or young of the desert cottontail and gambel's quail, thus its main food supply is only accessible for a restricted time duration every year. however, for this, the gila monsters exhibit three adaptations, which elevate their survival rate in the desert condition.  

first, is that they possess huge bodies, and can consume greater concentrations of food during a small period. secondly, they require to feed infrequently as they can accumulate fat in their tails. ultimately, their rate of metabolism is very low, so that they can burn their reservoirs of fat gradually.