Choice A is correct. In B, C, and E, the phrases beginning with not in place of no are wordy and unidiomatic. In D and E, the use of are presents a verb substitution problem: are can not take the place of the verb consider, as do can in A, because consider is something that people do, not something that they are. D and E thus fail to compare the attitudes of the two groups of people, referring instead only to how those in small towns and rural areas consider themselves. E also distorts the intended meaning by saying that people living in small towns and rural areas consider themselves less happy than people living in big cities. The question is of middle difficulty.