You are facing South on 2nd Street and turn East on Mustang Ave. The next one-way street you will reach is?

When you're facing South on 2nd Street and turn East onto Mustang Ave, you are now moving perpendicular to the street you initial faced. A typical street layout would have numbered streets running parallel to each other, typically in succession.

After making the turn onto Mustang Ave, which is running East-West, the next street you would encounter moving eastward would typically be the next numbered street, which is 3rd Street. In a typical grid layout, you would pass from 2nd Street, encounter Mustang Ave, and then immediately come to 3rd Street as the next eastbound one-way street.

The other options do not align with this street orientation. 1st Street would be located before 2nd Street, while 4th Street is after 3rd Street, making it the next one further down the line. Lastly, 2nd Street would not be reached again heading East after the turn onto Mustang Ave. Hence, selecting 3rd Street makes sense as the first one-way street encountered.