Which of these years did the NFL first play a game in London?

The NFL first played a game in London in 2007, but the option that aligns with the earliest start of the International Series, which included regular-season NFL games, is 2010. In fact, the first official regular-season NFL game held in London was on October 31, 2007, when the Miami Dolphins faced the New York Giants. However, since there seems to be some misunderstanding regarding the years presented in the options, 2010 was the year when a second game was played at Wembley Stadium, thereby marking the beginning of more consistent international games in London.

Understanding the NFL's efforts to expand its presence internationally is important; this was part of a larger strategy to increase the league's fan base globally and contribute to the growth of American football. As a result, the choice you’ve identified does not accurately reflect the NFL's initiation of games in London in terms of the first significant annual occurrence.