Solution:
In expressing a comparison, if two nouns refer to the same person or thing, the article is used before the first noun only. But if the nouns refer to different persons or things, the article is used before each noun. Since in the given statement, both the nouns dancer and singer refer to one person the article will be used before the first noun only and no article will be used before 'singer'. Also, the indefinite article 'a' should be used whenever someone's work or job is being referred to. Therefore Option D is the correct answer.

Solution:
The articles "a" and "an" are used to define singular forms of different objects or nouns. With words beginning with consonant sound 'A' article is used.

Solution:
In the first blank 'Ganga' is a specific river so 'the' article is used. On the other hand in the second blank 'river' is talked about which a general class therefore 'a' article is used.

Solution:
Definite article 'the' is used as an adverb before comparative degree. 'Higher' and 'Colder' are comparative degrees.

Solution:
'Heir' begins with a vowel sound and hence 'an' will be used.

Solution:
Here, the sentence talks about the 'letter' as general class of things. Since we are referring to general things, we need to use the definite article 'a'.

Solution:
'Elephant' is a word with vowel sound. Hence, 'an' article is used.