There is a sentence that is missing in the paragraph below. Look at the paragraph and decide where (option 1, 2, 3, or 4) the following sentence would best fit.

Sentence: Understanding central Asia’s role helps developments make more sense not only across Asia but in Europe, the Americas and Africa.

Paragraph: The nations of the Silk Roads are sometimes called ‘developing countries’, but they are actually some of the world’s most highly developed countries, the very crossroads of civilization, in advanced states of disrepair. ___(1)___. These countries lie at the centre of global affairs: they have since the beginning of history. Running across the spine of Asia, they form a web of connections fanning out in every direction, routes along which pilgrims and warriors, nomads and merchants have travelled, goods and produce have been bought and sold, and ideas exchanged, adapted and refined. ___(2)___ .They have carried not only prosperity, but also death and violence, disease and disaster. ___(3)___. The Silk Roads are the world’s central nervous system, connecting otherwise far-flung peoples and places…. ___(4)___. It allows us to see patterns and links, causes and effects that remain invisible if one looks only at Europe, or North America.

The correct option is Option 4.

To determine where the sentence best fits, let's analyze the sentence to be inserted and the context of the paragraph, especially around the insertion points.

Sentence to insert:
"Understanding central Asia’s role helps developments make more sense not only across Asia but in Europe, the Americas and Africa."

Analyzing the paragraph around option 4:
Before option 4, the text reads: "The Silk Roads are the world’s central nervous system, connecting otherwise far-flung peoples and places…."
Immediately after option 4, the text reads: "It allows us to see patterns and links, causes and effects that remain invisible if one looks only at Europe, or North America."

Logical Connection:
The sentence following option 4 begins with the pronoun "It". We need to find the singular noun phrase or concept that "It" refers to. If we place the sentence in option 4, the pronoun "It" directly refers back to the gerund phrase "Understanding central Asia’s role" (the act of understanding acts as a singular concept: "Understanding... allows us to see patterns...").
Furthermore, the inserted sentence mentions how understanding this role helps developments make sense across "Asia... Europe, the Americas and Africa", which is directly contrasted and completed by the next sentence explaining that it allows us to see patterns that remain invisible "if one looks only at Europe, or North America."

Therefore, the sentence fits most logically and grammatically at position (4).