Directions: After reading the passage below, fill in the blanks to make the passage coherent and grammatically correct. For the blanks with a given word, fill in each blank with the proper form of the given word; for the other blanks, use one word or phrase that best fits each blank.
Dogs haven’t always been man’s best friend, and the question of when and where they were first domesticated is surprisingly complex. A new study sheds some light on the issue; with an international team of scientists【小题1】 (point) to Central Asia as the best candidate for the origin of today's pups.
The study is 【小题2】 (expansive) one to date. It used three types of DNA 【小题3】 (gather) from 161 breeds of 4, 500 dogs, along with 549 “village dogs”—feral (未驯化的) dogs 【小题4】 make up an estimated 75 percent of the world’s total dog population—from 38 countries.
While it's long been known that dogs can trace their roots to gray wolves, the new analysis is the strongest indicator yet that modern dogs originated in 【小题5】 is now Nepal and Mongolia over 15,000 years ago. The DNA of dogs in nearby areas like East Asia and Southwest Asia is extremely diverse, giving the scientists confidence 【小题6】 (make) the claim.
However, 【小题7】 the study is impressive for its extensiveness, the scientists are cautious about making a definitive statement on dogs' origins. Previous studies 【小题8】(place) dogs’ ancestral tree (族谱) in other regions like Siberia and Europe. Adam Boyko of Cornell University, one of the study’s researchers, called the origins of modern dogs “extremely complicated”. He said that it was possible that dogs were domesticated elsewhere 【小题9】 arriving in Central Asia and diversifying into modern dogs.
Anyway, the study’s large population sample is remarkable, representing a clearer picture of dogs and 【小题10】 they come from.