Answer:
3. finer than that of the Metropolitan Museum of Art in New York.
Step-by-step explanation:
This is talking about comparatives (like "better", "greater", "worse", etc) and superlatives (like "best", "greatest", "worst", etc).
Remember that whenever we use a comparative or a superlative, we never add the word "more" to it; doing so is redundant and makes the sentence run choppily. So eliminate 2.
Read sentence 1. Grammatically, it's correct; however, if we put it into the sample sentence:
"In my opinion, the art collection of the Louvre in Paris is finer than the Metropolitan Museum of Art in New York"
This makes it sound like the art collection of the Louvre is finer than the actual museum in New York, which is probably not the comparison we want to make. Instead, we want to compare the art collection of the Louvre with the art collection of the Met. So eliminate 1.
Thus, the answer is 3, which runs smoothly and makes sense.