Answer:
b. Vernalization
Explanation:
Vernalization is a phenomenon in which plants require low temperature for the flowering. There is either qualitatively or quantitatively dependent on exposure to very low temperature. This process is known as vernalization. Vernalization defines especially to the promotion of flowering by a period of low climate. For example; Vernalisation occurs in biennial plants. Biennials are monocarpic plants which normally flower and may die in the second season. Some common examples of biennials are carrots, Sugarbeet, cabbages, etc.
Bottlenecks and founder effects. Genetic drift can cause big losses of genetic variation for small populations. Population bottlenecks occur when a populations size is reduced for at least one generation... reduced genetic variation from the original population
This is called Subsistence Hunting
Competition of resources, predation or disturbances (man-made and natural)
