The correct answer is: C. Either I or II is implicit.
The statement does not provide enough information to determine whether or not people desire to keep their city clean, or whether or not the Civil Council has failed in its campaign. It is possible that people do desire to keep their city clean, but that the Civil Council’s campaign was not effective in reaching them. It is also possible that people do not desire to keep their city clean, and that the Civil Council’s campaign was not effective in changing their minds.
Therefore, either assumption I or assumption II could be implicit in the statement.