The Mature stage is the most dangerous phase of a thunderstorm. Endospores in a Bacillus cell culture are most prevalent in the death phase. The diploid zygote forms when the sperm nucleus and egg nucleus fuse. The correct answer is option B.
The most dangerous stage of a thunderstorm is the Mature stage, which begins after the cloud has fully developed into the cumulus stage and entered the mature phase where updrafts and downdrafts coexist. During this phase, the storm is most likely to produce heavy rains, lightning, strong winds, hail, and sometimes tornadoes, making it the most dangerous phase of the storm's life cycle.
In a Bacillus cell culture, the most endospores can be expected during the death phase. Endospores are a survival mechanism for bacteria, and their formation is triggered by adverse conditions such as the depletion of nutrients, which typically occurs in the death phase of bacterial growth.
The diploid zygote forms when the sperm nucleus and the egg nucleus fuse (option b). This is the moment of fertilization when genetic material from both parents combines to form a new organism with a full set of chromosomes.
Therefore, option B is correct.