**Explanation:**

When forming the plural of compound nouns, such as "father-in-law," the general rule is to make the main noun plural. In this case, "father" is the main noun, and "in-law" is the modifying phrase. Therefore, the correct plural form is "fathers-in-law."

Let's break down the explanation further:

**Compound Nouns:**
Compound nouns are made up of two or more words that function as a single unit. In this case, "father-in-law" is a compound noun formed by combining the words "father" and "in-law."

**Pluralizing Compound Nouns:**
To form the plural of compound nouns, we generally make the main noun plural. In this case, the main noun is "father," so it becomes pluralized to "fathers."

**Modifying Phrase:**
The phrase "in-law" serves as a modifier to the main noun "father." It indicates the relationship of the person being referred to as the father-in-law. The modifying phrase is not pluralized; it remains in its singular form.

**Placement of the Plural Marker:**
The plural marker, which is the letter "s," is added to the main noun "father." It is placed after the noun and before the modifier. Therefore, we get "fathers-in-law" as the correct plural form.

**Summary:**
In summary, the plural of "father-in-law" is "fathers-in-law" because the main noun "father" is made plural, and the modifying phrase "in-law" remains singular. This follows the general rule of forming plurals for compound nouns.

Explination : father in law is in singular form so when there are 2or more father in law so we write and say as fathers in law as they are father so we call fathers in law