The D.C. Preservation League unveiled its 2009 Most Endangered Places list yesterday. The one modern building on the list was no surprise: the Third Church of Christ, Scientist at 900 16th St. NW. The Brutalist-style church, built in 1971, made the list last year as well. The city recently said the church, which was designated a D.C. landmark, could be demolished. A developer plans to do just that and build an office building. DCPL plans to appeal the decision and is having an event June 20 to discuss how to adapt the landmark building for use today.