Concrete nouns are nouns which can be experienced through one/more of our five senses viz. sight, smell, hearing, touch and taste.
Option A: The word "I" is a pronoun and not a noun. Hence this is not the correct answer.
Option B: The option "respect" is an abstract noun. We cannot see/ smell/ hear/ touch/ taste respect. It is a feeling. Hence, it is not a concrete noun.
Option C: The word "my" is a possessive adjective. Hence this is not the correct answer.
Option D : The word " teachers" refers to a more than one persons who teach. We can see our teachers. Hence this is a concrete noun.
Tip: The word "teachers" is a common noun. All common nouns are concrete nouns. This is another way to find the answer.