Use the Following Information When Answering the Corresponding Question(s)

Use the following information when answering the corresponding question(s) .
Researchers found that high doses of nitric oxide were not lethal to soybean cells.Likewise,high doses of reactive oxygen intermediates were not lethal to soybean cells.However,when combined,nitric oxide and reactive oxygen intermediates were very lethal to soybean cells.(M.Delledonne et al.2001.Signal interactions between nitric oxide and reactive oxygen intermediates in the plant hypersensitive response.Proceedings of the National Academy of Sciences,USA 98(23) :13454-59. )
-Refer to the paragraph on Delledonne et al.Why would the researchers study the association between cell death,nitric oxide,and reactive oxygen intermediates?

A) to gain insight into how R genes are inherited
B) to gain insight into how R proteins recognize avr proteins
C) to gain insight into what happens after R-avr protein binding
D) to gain insight into how pathogens kill plant cells