Answer an analysis: this question can start from the second space, and the words filled in match with "heart" and correspond to "plain". Item A "doesn't matter" describes a calm mood, pays little attention to it, is properly matched and conforms to the context. Item b "boring" is described as boring, uninterested, negative and inconsistent with the meaning of the text, so it is excluded. Item C "Enron" describes carefree, which is very reassuring. The article does not emphasize worry-free, and it is not properly matched with "heart" and is excluded. Item d "Qing" means clear and definite, and it is not properly matched with "heart" and is excluded.

The first empty substitution verifies that "ordinary" and "landscape" are properly matched and conform to the meaning of the text.

So the correct answer is a.