Correct Answer: narrow

Solution : The fourth option is the correct choice.

The sentence begins by stating that the main street is "neither broad nor", indicating a comparison between two contrasting characteristics. Narrow refers to something having a limited width or extent, emphasising a lack of breadth. On the other hand, broad denotes a large extent from side to side, emphasising breadth and spaciousness.

The meanings of the other options are as follows:

• Shallow means having little depth, often used in the context of water or knowledge.
• Wide means having a great extent from side to side; broad.
• High means measuring a great vertical extent; tall or elevated.

Therefore, the complete sentence is: "The main street, which is neither broad nor narrow , runs past this square on its way to the railway station."