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 first and second blank shall take the indefinite articles 'an' and 'a' respectively because the first blank is followed by a word starting with the vowel 'i' and 'interesting book' represents a singular countable noun and the second blank is followed by 'wonderful picture' which represents a singular countable noun and is followed by a word starting with the consonant 'w'.
The third blank shall take 'the' as the sentence talks about Victorian people which shows particularity. The fourth blank won't take any article as 'Victorian times' is uncountable and represents no specific time.
The correct answer is C) an/a/the/ noarticle.
It is an interesting book. It gives a wonderful picture of what the life was like in Victorian times.