How would the plants in a specific environment be impacted if there was a sudden drop in the amount of bacteria present in that area?

The plants in a specific environment get influenced if there was a sudden reduction in the number of bacteria present in that region, that is, there are both negative and positive consequences related to this situation.

Positive: The reduction in bacterial colonization will protect the plants from the diseases, which are caused by the bacteria, and this will encourage better growth of the plant. Like bacterial canker in tomato, black rot in Brassica resulting due to Xanthomonas campestris, and others.  

Negative: The plants remain in symbiotic association with bacteria in order to attain impermeable inorganic minerals from the soil. When the amount of bacteria becomes nil or low, the plants will not be able to attain these nutrients, and their development may get hampered. For example, bacteria help to fix atmospheric nitrogen, that is, taken up the root nodules of the leguminous plants. In return, these bacteria get the desired food from the plants.  

answer; i believe that the correct answer is (light);

i think a) betsy can donate only blood to mark is correct because, mark and betsy have the same blood type. whereas nobody else has b+ blood so betsy can't donate to them.