Question 513General Subjects - Assistant Engineer

The correct answer is D) threaded with national coarse threads. The letters "NC" in "1/4-20 NC" refer to the thread designation "National Coarse," which is a standard thread type used in the United States. The "1/4-20" indicates the bolt diameter (1/4 inch) and threads per inch (20). So, the "NC" designation specifically means the bolt is threaded with the national coarse thread pattern, which is a common thread type used in many industrial and mechanical applications. The other answer choices are incorrect because they do not accurately describe the meaning of the "NC" designation in the bolt specification.