The correct option is B A
An indefinite article is used when we are talking generally about something whereas a definite article is used when we are talking about something specific.
The indefinite articles are 'a' and 'an'. An is used before a word starting with a vowel or vowel sound. A is used before a word starting with a consonant or consonant sound.
A definite article is an article that tells the uniqueness of something.
'The' is the only definite article .
The blank shall take 'a' as 'book' is singular countable noun ans starts with the consonant 'b'.
The correct answer is B) A.
I want a book from the library.