Task: Question Answering
Input (English): Background Paragraph: Apex predators can have profound effects on ecosystems, as the consequences of both controlling prey density and restricting smaller predators, and may be capable of self-regulation. They are central to the functioning of ecosystems, the regulation of disease, and the maintenance of biodiversity. When introduced to subarctic islands, for example, Arctic foxes' predation of seabirds has been shown to turn grassland into tundra. Such wide-ranging effects on lower levels of an ecosystem are termed trophic cascades. The removal of top-level predators, often through human agency, can cause or disrupt trophic cascades. For example, reduction in the population of sperm whales, apex predators with a fractional trophic level of 4.7, by hunting has caused an increase in the population of large squid, trophic level over 4 (carnivores that eat other carnivores). This effect, called mesopredator release, occurs in terrestrial and marine ecosystems; for instance, in North America, the ranges of all apex carnivores have contracted whereas those of 60% of mesopredators have grown in the past two centuries. 
Story: John was studying the species in Siberia. He found that the Siberian tiger is an apex predator. It had a pretty stable population during the sixteenth century. He noted that information as case A. Then with the introduction of guns the number of Siberian tigers decreased in the seventeenth century. He noted that information as case B. 
Question: In which case biodiversity would decrease, case A or case B?
Output (English): case B.