What is the location of the NYCTA rapid transit tunnel under the East at 34th street?

The correct location for the NYCTA rapid transit tunnel under the East River is at 34th Street. This is significant because the East River tunnels are integral to the transit connections between Manhattan and the boroughs, serving various lines such as the 6 train and others.

The choice of 34th Street is relevant as it is a major thoroughfare in Manhattan and the site of several transit hubs. The tunnels run directly beneath this street, facilitating the movement of passengers and connecting several neighborhoods. Moreover, 34th Street is well-known for its proximity to key locations, including the Midtown area, making it a central point in the transit system.

The other options represent streets that are either farther away from the tunnel's actual location or not directly associated with major transit routes under the East River. For instance, streets like 20th or 40th Street do not have tunnels associated with the rapid transit system running directly beneath them, thus reinforcing why 34th Street is the accurate choice.