Hi Mohammad, As a pronoun, "it" is used to refer to singular nouns. Let me use your examples to form some complete sentences: A: It's the roses that I love. B: It's the cities that draw the most talent. In such cases, the "It" is something like an anticipatory "It". In A, "It" means "What I love" (What I love is the roses.) In B, "It" means "What draws the most talent" (What draws the most talent is the cities.) As you can see, "is" is still used in A and B because we are focusing on a SINGLE idea. In A, the single idea is "What is the one thing I love?". So, What I love IS.... The same logic applies to B. In B, the single idea is "What single criterion draws the most talent?" So, What draws the most talent IS... To elaborate a little further with another example, the "It" in the sentence "It is a beautiful day." is an anticipatory "It". It helps the reader to anticipate a noun. In this case, the noun is "day". In a way, yes, "it" can refer to many nouns, but it refers to many nouns as a SINGLE group. Example: The judge asked the jury for ITS verdict. I hope this helps.

Yes, you can use (it) with singular and plural.

its = belonging to it (singular possessive) it's = it is (singular subject + verb to be) . No idea what "it's times" would mean. It's time to answer the question. = It is time to ... It's cities that will be the future. = It is (the concept is that) cities will ... . Its suburbs stretched as far as the eye could see. = It (the city?) 's (possessive) suburbs (belonging to it, the city, singular) stretched ...