Change the degree of comparison to positive without changing the meaning of the sentence.
That is the oldest city in the country.
A)No other city in the country is as old as that one.
B)That is the city that is older than the others in the country.
C)The city is not younger than the others in the country.
D)That is the youngest city in the country.

Hint: The degrees of comparison of the word good is good (positive), better (comparative), and best (superlative).

Complete step-by-step answer:

The degree of comparison indicated by their form in what degree of intensity the quality described by the adjective exists.
There are three degrees of comparison :
1)The Positive Degree of Comparison, which has the simplest form of the adjective and has no special ending. It merely describes the quality, without suggesting or expressing any comparison.
2)The Comparative Degree of Comparison, which is formed by adding the suffix “er” to a positive degree. It denotes the second degree of comparison.
3)The Superlative Degree of Comparison, which is formed by adding “est” after the positive degree, or at times, “most” before the positive degree of comparison. It denotes that the quality exists in the highest degree of the object described.
In the given question, we have to change the degree of comparison to positive, without changing the meaning of the sentence. The given sentence is “That is the oldest city in the country”, this sentence is clearly in a superlative degree form, as we can see the word “oldest” in it, which has the suffix “est”. To find out if the sentence is in a positive degree of comparison, we will find the first degree of the word “oldest”, which is “old”. Here, only option 'a' has the word “old” in it. All the other options are either grammatically incorrect or not in a positive form of degree. Hence, the correct answer is, option a.

Note: When more than two persons/things are compared, we use a superlative degree of comparison.