Choice B is the best answer because the context makes clear that the clustering of jobs, innovation, and productivity will be more concentrated in, or more densely packed into, “a smaller number of bigger cities and city-regions” (line 39).

Choice A is not the best answer because although “intense” sometimes means “emotional,” it would make no sense in context to say that the clustering of jobs, innovation, and productivity will be more emotional in “a smaller number of bigger cities and city-regions” (line 39).

Choice C is not the best answer because although “intense” sometimes means “brilliant,” it would make no sense in context to say that the clustering of jobs, innovation, and productivity will be more brilliant in “a smaller number of bigger cities and city-regions” (line 39).

Choice D is not the best answer because although “intense” sometimes means “determined,” it would make no sense in context to say that the clustering of jobs, innovation, and productivity will be more determined in “a smaller number of bigger cities and city-regions” (line 39).