The preparation and flowering of leaves of tea and tobacco is due to the activities of Bacillus subtilis, Streptococcus lactis, Acetobacter aceti, and Bacillus megatherium.

The bacteria Bacillus megatherium is the gram-negative bacteria. It is spore-forming bacteria found in the soil in diverse habitats. These bacteria have the ability to promote plant growth. It increases the drought or salt tolerance in the plants like tobacco and tea. They also reduce the chance of diseases in these plants. So, the correct answer is option B.