Which claim is the narrowest and most focused?

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

21 balloons is the story of professor william sherman's travels.

in 1883, he set off from san francisco for a balloon ride over the pacific and was found a month later floating with 21 balloons in the atlantic ocean. this seemed an astounding feat and everyone wanted to know what had happened.    

professor sherman was loyal, however, and said he would tell his tale first to the western american explorers club in san francisco, of which he was a member. this built up suspense for several chapters before he began to tell of the wonders of his adventures and the amazing island of krakatoa, an island which had just been blown up by a volcano.  

the residents of krakatoa are all millionaires who live under a "gourmet government" of their own devising. we get to see all the incredible adventures that creative people with unlimited resources would create according to the author.

one of the central themes of edward abbey's work has been his staunch opposition to the glen canyon dam on the colorado river that created lake powell, destroying stunning scenery and wildlife habitat, endangering many rare species of fish and animals, and also irreparably destroying many important archaeological sites which provided information about the early inhabitants of the united states.

which detail from "home place retold" supports the central idea that despite physical changes, watonwan is a special place for generations of people?

great great-grandchildren retell the story of early days. .

young families worked hard to build a life.

those matches might seem surprising in modern times.

in 1881, more than 50 such families fled religious persecution. .