I belive the answer is B.
Formal language is also called "proper language" because it is the type of language you would use when first meeting someone or giving a speech at a high class place so the correct answer is:
<span>B) Have I convinced you that the study of grammar is important and well worth your effort? </span>
This is true, you always need to analyse what work youre going into "ALL ASPECTS"
Forgot to include the text!
