Read the sentence carefully and select the most appropriate option to substitute the underlined part.
The sudden declaration of war between two countries led to a disarray.

The correct option is disorderly situation.

Explanation:

The word disarray refers to a state of disorder, confusion, or chaotic mess.

Let's analyze the given options to find the most appropriate substitution for the underlined word:

1. elusive situation: "Elusive" means difficult to find, catch, or achieve, which does not match the meaning of "disarray".
2. peaceful treaty: "Peaceful" is antonymous to the context of a sudden declaration of war.
3. refined argument: "Refined" means elegant or cultured, which is irrelevant to chaos or confusion.
4. disorderly situation: "Disorderly" means lacking organization, confused, or untidy, which perfectly conveys the meaning of "disarray".

Therefore, replacing disarray with disorderly situation makes the sentence grammatically correct and logically accurate in context.