**Rule: The indefinite article 'a'/'an' is used before singular countable nouns that denote a profession.** 'Surgeon' is a profession. Since 'surgeon' starts with a consonant sound, 'a' is the correct article to use. 'An' would be for a vowel sound. 'The' would imply he is the only surgeon or a specific surgeon already known. 'No article' is incorrect as a profession needs an article.

**Rule: The definite article 'the' must be used before a superlative degree of an adjective.** 'Tallest' is the superlative form of 'tall'. Since it singles out one person from the group ('in the class'), it is definite and requires 'the'. Options (a), (b), and (d) are grammatically incorrect before a superlative.

**Rule: No article is generally used before the names of diseases.** We say 'suffering from cancer', 'suffering from malaria', 'suffering from diabetes'. However, there are exceptions, and for some pains or non-serious illnesses, 'a' is used (e.g., 'a cold', 'a headache'). For serious diseases like cancer, no article is the standard. Options (a), (b), and (c) are incorrect.

**Rule: The definite article 'the' is used before the names of newspapers.** 'The Times of India', 'The Guardian', 'The New York Times' are all proper names of newspapers and require 'the'. Options (a), (b), and (d) are incorrect.

**Rule: The definite article 'the' is used before the names of canals.** Similar to rivers and oceans, canals are specific geographical features that require 'the'. Examples include 'the Suez Canal' and 'the Panama Canal'. Options (a), (b), and (d) are therefore incorrect.

**Rule: The abstract noun 'pity' takes the article 'a' in the expression 'it is a pity'.** This is a fixed phrase used to express regret. 'Pity' in this construction functions like a singular countable noun. Option (b) would imply a specific, known pity. Option (c) is wrong by sound. Option (d) is incorrect for this idiom.

**Rule: Use 'a' before singular count nouns used with 'pair of'.** Even though 'shoes' is plural, the head noun of the phrase is the singular 'pair'. Therefore, the article must agree with 'pair'. 'New' starts with a consonant sound, so 'a' is correct. Option (b) is wrong by sound. Option (c) would mean a specific pair. Option (d) is not typically used with 'pair of' in this singular context.

**Rule: Certain abstract nouns in fixed expressions take 'the'.** 'Speak the truth' and 'tell a lie' are fixed idiomatic expressions. In 'speak the truth', 'truth' is considered a unique, definite concept. Therefore, 'the' is always used. Options (a), (c), and (d) are incorrect for this fixed phrase.

**Rule: The definite article 'the' is used before the names of deserts.** Just like with oceans and rivers, the names of deserts (e.g., the Sahara, the Gobi, the Mojave) are preceded by 'the'. Options (a), (c), and (d) are incorrect.

**Rule: The indefinite article 'a' can mean 'per' in expressions of rate, frequency, or price.** In this sentence, 'a month' means 'per month' or 'each month'. This is a standard use of the indefinite article. Option (b) is wrong by sound. Option (c) would refer to a specific month. Option (d) would be ungrammatical.