The New York City Marathon is this Sunday, and it is shaping up to be an exciting race, partly because defending champions Mary Keitany and Lelisa Desisa (who won the marathon at the recent World Championships in Doha) will be back, but also because of the long list of Americans (especially on the women’s side) who will be looking for their spot in the Olympic Marathon Trials in Atlanta on February 29. To qualify, they must run the B standard…