We know that there square measure 3 degrees of comparison, namely, positive, comparative, and superlative. we will use every of those degrees of comparison during a sentence, betting on its context.
A positive comparison is achieved once someone or Associate in Nursing object is on their own and not being compared with the rest. E.g. The climate of metropolis is gentle.
A comparative comparison is achieved once someone or object is being compared with another person or object. E.g. The climate of metropolis is milder than the climate of city.
A superlative comparison is achieved once someone or Associate in Nursing object is deemed to be the sole one in every of its kind among a gaggle of persons or objects. E.g., The climate of metropolis is that the mildest of all.
Let us contemplate the higher than question - The climate of metropolis is milder than city.
Here, we've got to check the climates of the 2 cities. This makes it a comparative sentence. In comparative sentences, the adjective is followed by the suffix ‘er’ or it's preceded by the word ‘more’. during this case, gentle becomes milder. because the word becomes milder, it won’t be preceded by additional. Therefore, possibility ‘d’ The climate of metropolis is milder than that of city, is that the correct answer.