TASK DEFINITION: Generate the answer for a given question. The question requires common knowledge of English. Make sure that the answer is in detail, long, consistent with the context, and requires general knowledge of English. To be less repetitive, please vary your language for each question. Give a proper explanation to answer, and if necessary, provide the definition of various terms. And conclude your answer if it's long. If you have used other resources (e.g., Merriam Webster's.) to answer the question, include citations in your answer. You don't need to paraphrase the context of your resources, but make sure that your answer is consistent and complete.
PROBLEM: What did 'Four-F.' mean in the United States of the 1940s? Here is the quote from Catch-22: They had to send a guy from the draft board around to look me over. I was Four-F. I had examined myself pretty thoroughly and discovered that I was unfit for military service.

SOLUTION: It's a classification for military service. 4-F means 'Registrant not acceptable for military service.' The context clue here you might have used to deduce an area of inquiry would be the reference to a 'draft board', which is part of the Selective Service System that determines the eligibility and thus the classification of potential draftees.

PROBLEM: Can one use kindness as a synonym for politeness? What's the difference? Where do you draw the line between them?.

SOLUTION: I think this is a situation in which etymology is revealing. The background of polite, according to the Online Etymology Dictionary, is: mid-13c., from L. politus 'refined, elegant,' lit. 'polished,' pp. of polire 'to polish, to make smooth.' Used literally at first in English; sense of 'elegant, cultured' is first recorded c.1500, that of 'behaving courteously' is 1762. Polite, both in its original literal usage and in its current usage, is more about superficial appearance. To be polite, one need only use polite words and manners. Nothing internal is necessary. The history of kind, on the other hand, is related to internal goodness: 'friendly,' from O.E. gecynde 'natural, native, innate,' originally 'with the feeling of relatives for each other,' from P.Gmc. gakundiz, from kunjan (see kin), with collective prefix ga- and abstract suffix -iz. Sense development from 'with natural feelings,' to 'well-disposed' (c.1300), 'benign, compassionate' (c.1300). Ultimately, politeness tells you little about a person's character; it may be sincere, or it may be highly calculated. Kindness, though, is directly related to a person's character, and is quite difficult to fake.

PROBLEM: Are both is equal to and equals similar in meaning? Which is the more natural? For example, one plus one equals two or one plus one is equal to two.

SOLUTION:
Both are grammatically correct and mean the same. And both are the natural ways of saying it. Use either.