reducing greenhouse gas emissions was a major goal of this week's paris climate talks. it brings me to my question of the week. which of the following cities is the most congested in the world? loss ang less, beijing, istanbul, or mexico city? stay tuned and we'll tell you the correct answer. this week's book of the week is "who speaks for islam?" "what a billion muslims really think" by john esposito and dahlia mogahead. you hear a lot these days about muslims and what they believe. here are the facts provided by two experts on islam who have combed through opinion polls, surveys and election results. in today's charged atmosphere, this book provides an essential voice of calm and reason. the correct answer to the gps challenge question is c.