What is the ICAO code for Washington Dulles?

The ICAO code for Washington Dulles International Airport is indeed KIAD. ICAO codes are four-letter alphanumeric codes assigned by the International Civil Aviation Organization to identify airports worldwide. The first letter represents the region and country of the airport. In this particular case, "K" indicates that the airport is located in the United States, and "IAD" stands for Dulles International Airport specifically.

When looking at the other choices, KDAL refers to Dallas Love Field, KWAH is not an assigned code for any known airport, and KDEN represents Denver International Airport. Thus, KIAD is correctly identified as the ICAO code for Washington Dulles because it follows the established conventions for designating U.S. airports and is specifically designated for that location.