The over-prescription of antibiotics since the 1940s has promoted the evolution of antibiotic resistant strains of many bacterial infections. this process can best be described as what kind of evolutionary force? (genetic bottleneck, genetic drift, founder's effect, natural selection, directional pressure.)

Antibiotics are the medicines which prevent and treat the bacterial infections by inhibiting their growth. Antibiotic resistance is the potential of a bacterium to withstand the effects of an antibiotic. It is a consequence of evolution through the process of natural selection. It occurs through the genetic mutation and the bacteria evolve through natural selection. The widespread use of the antibiotics has made many bacteria resistant through the process of evolutionary pressure driving natural selection. The bacteria carrying the genetic mutation of antibiotic resistance survive and reproduce passing the trait to their offspring.  

answer: ice crystals in air

the water from the water body or another source of water gets evaporated as water vapor as an effect of heat on water. these water vapor rises in the upper layers of the earth atmosphere under high atmospheric pressure. the atmospheric pressure of these water molecules starts to decrease due to the effect of cold air. the invisible water vapor condenses into visible water droplets and ice crystals.these ice crystals and water droplets being less denser than the surrounding air floats on air as clouds.

burning fossil fouls really decrease the carbon in the atmosphere so b