Situation: The effects of chemical fertilizers on the production of grain and vegetables is discussed in relation to the country of Illina.
Reasoning: We need to find the basis for the contrast discussed between the production of food grains and vegetables.
(A) Incorrect: This option does not explain the relationship between chemical fertilizers and vegetables, which is integral to the difference in production.
(B) Incorrect: The parallel effects in productivity changes are not an explanation of the contrast in production of food grains and vegetables.
(C) Incorrect: The authenticity of the data set is an external idea and does not have a bearing on the contrast in food production.
(D) Correct: This option explains the basis for the reduction in the production of vegetables and the contrasting increase in grain production.
(E) Incorrect: The origin of the vegetable crops is an external idea that is not mentioned and cannot explain the contrast without additional information.
E is the correct answer.