Select the most appropriate option that can substitute the underlined segment in the given sentence. If there is no need to substitute it, select ‘No substitution’.
In yesterday’s fire accident, her feets are burnt badly.

The correct option to substitute the underlined segment is "her feet were".

Let's break down the rules of English grammar that apply to this sentence:
1. Noun Pluralization: The noun "foot" is an irregular noun. Its plural form is "feet", not "feets" or "foots". Therefore, "feets" in the original sentence is grammatically incorrect.
2. Subject-Verb Agreement: The subject "feet" is plural. Therefore, it requires a plural verb.
3. Verb Tense: The sentence refers to an event that happened in the past ("yesterday’s fire accident"). Thus, we must use the past tense plural verb "were" instead of the present tense "are" or singular past tense "was".

Combining these corrections, the segment "her feets are" must be replaced with "her feet were" to make the sentence grammatically correct: "In yesterday's fire accident, her feet were burnt badly."