<u>Answer</u>: c. a and b
Trees play vital roles in the production of oxygen as well as the fixation of carbon from 
. As trees use nitrogen, phosphorus and water as nutrients for growth, their diminishing numbers would change the balance between these three elements significantly.
Thus, during rains, the water level will rise much faster and higher in the absence of trees. These could possibly lead to increasing cases of devastating landslides.
C)
The difference between allele A and allele S is due to changes in the environment.
Answer:
The substance moves from low to high concentration, against the concentration gradient.
Explanation:
When molecules move from high to low concentration, it is known as Diffusion. It moves with the concentration gradient and does not require energy.
However, when molecules move from low to high concentration, it is against the concentration gradient and cannot proceed without Energy. This process is called Active transport.
Cell membrane is not thick, it is thin and semi permeable.
