C, the first two don't make sense and the last one would support the opposing view point.
B is the correct answer. They can sometimes show an extinction but not always.
Reproductive isolating mechanisms are barriers which impeded mating (prezygotic) or prevent the hybrid from developing properly (postzygotic) but the overall effect is to cause speciation by making it difficult for two diverging species to share genes. So one kind of mechanical isolation could be the usage of contraceptives. As of temporal isolation, or behavioral isolation could be exemplified by people who suffer from diseases that cause separation (such as HIV or cancer). I hope that this is the answer that you were looking for and it has helped you.
As the bear enters hibernation, its metabolic processes such as body temperature, heart rate, and respiratory rate are reduced. But bears do not lower the body temperature as much as once thought. Their hibernation temperature is around 88 degrees and waking temperature is 100 degrees F. This relatively high sleeping temperature allows bears to become fully alert if aroused, perhaps to enable the bear to protect itself from predators and other dangers without unnecessarily taxing their energy reserves. Over the course of a hibernating season it is thought that bears use approximately 4 thousand calories a day, which results in a weight loss of about 20 percent of it body weight by spring.
