Which claim is the narrowest and most focused? a. hydraulic fracturing is not as dangerous as people think, and natural gas is an important byproduct. b. mandatory voting makes it harder for extremists to get elected in australia; it should be required in the united states. c. standardized tests are often difficult for students, and they are a tried-and-true way to assess one's skills. d. because of advances in medical care, airline pilots should be allowed to work beyond the age of 60.