To determine the characteristic of Wide Area Networks (WANs) from the given options, let's analyze each statement:

1. Option 1: "WANs are always public networks managed solely by Internet Service Providers (ISPs)."

   This statement is incorrect. While many WANs are public and managed by ISPs, organizations can also manage their own private WANs. Thus, WANs are not always public networks.

2. Option 2: "WANs typically use only wireless media to connect distant LANs."

   This statement is incorrect. WANs use a variety of media including both wired (such as fiber optic cables) and wireless technologies. They are not limited to wireless media alone.

3. Option 3: "WANs are limited to connecting devices within a radius of 1 to 2 km."

   This statement is incorrect. WANs are designed to cover much larger geographic areas than Local Area Networks (LANs) and can span cities, countries, or even continents.

4. Option 4: "WANs can be built by connecting multiple LANs via wired or wireless links."

   This statement is correct. WANs are created by interconnecting multiple LANs through various types of links, which can be either wired or wireless. This allows them to connect LANs that are located far apart from each other.

Based on the analysis above, the correct statement describing WANs is: "WANs can be built by connecting multiple LANs via wired or wireless links." This accurately reflects their ability to interconnect different LANs over a wide geographical area using a variety of transmission media.