Explanations:In English grammar, adjectives are used to describe nouns and can be modified to express comparisons. There are three forms of adjectives: the positive (or base) form, the comparative form, and the superlative form. The positive form is used to describe a noun without making any comparison. The comparative form is used to compare two entities, and the superlative form is used to compare more than two entities.
The adjective "big" is a positive form that describes the size of something. When we want to compare two entities, we use the comparative form "bigger." For example, "Kolkata is bigger than Mumbai" compares the size of Kolkata and Mumbai. The superlative form "biggest" is used when comparing more than two entities, such as "Kolkata is the biggest city in the state of West Bengal."
In the given sentence, "No other city in India is so _____ as Kolkata," the structure of the sentence does not indicate a comparison with more than two cities. The phrase "No other city in India" suggests that Kolkata is being described as big without making a comparison to other cities. Therefore, the correct form to use is the positive form "big."
It is important to note that the sentence structure and context are crucial in determining which form of the adjective to use. In this case, the sentence is describing Kolkata as big without making a comparison to other cities, so the positive form "big" is the correct choice.