Which avenue is not mentioned as being paired with a numerical designation?

The correct answer, which identifies the avenue not mentioned as being paired with a numerical designation, is 1st Ave. In urban planning and transportation references, avenues are often organized numerically and sometimes may allow for changes or omissions in the designations. The other options, such as 3rd Ave, 6th Ave, and 5th Ave, are frequently referenced in conjunction with their numerical identifiers within urban contexts and public transport routes. Thus, 1st Ave may not be associated in the same frequency or context as the others, reinforcing its distinction from those that clearly carry a numerical designation in these discussions.