Explanation:

- The sentence talks about the establishment of the East India Company by merchants in the year 1600.

- Each option represents a different grammatical structure to complete the phrase "came together in the year 1600".

- Option 1: "to form"

- This option implies the purpose of the merchants coming together, which was to establish the company.

- This matches the purpose-driven nature of the sentence.

- This is the correct choice.

- Option 2: "formed"

- This indicates that the merchants had already established the company, but that's not consistent with the 'coming together' action.

- Option 3: "formed"

- Same as Option 2, this doesn't convey the intention but rather the result.

- Option 4: "to forming"

- This is grammatically incorrect; after "came together," an infinitive form like "to form" is required.