Important weather phenomena occur mostly in the a. thermosphere b. stratosphere c. mesosphere d. troposphere

The answer is:

Troposphere

Here is more about your question:

The Earth's atmosphere is divided into layers and the troposphere is the first layer. This layer is where we live in. This layer also has the most moisture among all the layers and this is why most clouds and weather occur in this layer. The other layers have very little moisture.

The features of the mesosphere would be the ice crystals that form there because it is so cold. The ice crystals help protect the Earth from meteors and other space junk. The stratosphere is the layer that contains our ozone layer. The thermosphere is the outermost layer, which contains the ionosphere and the exosphere.

many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.