Pronoun has to agree with the case. Here, it is the objective case. So, 'me' should be used instead of 'I'. "Me" is an object pronoun, which means that it serves as a direct or indirect object to the verb or as the object of a preposition.

Hence, option B is the correct answer.

Pronoun has to agree with the case. Here, it is the subjective case. So, 'I' should be used instead of 'me'. "I" is a nominative pronoun, which means that it is used as the subject of a sentence, or as a predicate nominative.

Hence, option A is the correct answer.

The complement of the verb 'be', when it is expressed by a pronoun, should be used in the nominative form.

Hence, 'him' should be replaced with 'he' to form a grammatically correct sentence.

Therefore, option A is the correct answer.

When the pronouns used in the subjective case are in plural, the order of pronouns should be 123 i.e. it should be 'We, you, and they' to form a grammatically correct sentence.

Hence, option A is the correct answer.

'Who' is used in the nominative case while 'whom' is used in the objective case.

Here, 'who' should be placed with 'whom' to form a grammatically correct sentence.

Hence, option A is the correct answer.

When the subject of a verb is a relative pronoun, the verb should agree in number and person with its antecedent.

Here, the antecedent of 'that' is 'theories' and not 'one'. Hence, 'has' should be replaced with 'have' to form a grammatically correct sentence.

Therefore, option C is the correct answer.

If a relative pronoun has two antecedents, it should agree with the nearer one.

'Which' should agree with 'everybody'. Therefore, 'which' should be replaced with 'who' to form a grammatically correct sentence.

Hence, option B is the correct answer.

'Anyone' should be used when more than two persons or things are spoken of. Hence, 'either' should be replaced with 'anyone' to form a grammatically correct sentence.

Therefore, option B is the correct answer.

There is used as an adverb meaning ‘in, at, or to that place or position’ while ‘their’ is a possessive pronoun used to describe something ‘belonging to or associated with the people or things previously mentioned or easily identified’.

Therefore, ‘there’ must be replaced with ‘their’ to form a grammatically correct answer.

Therefore, option B is the correct answer.

After the word 'let', pronouns are always used in objective case.

Therefore, ‘I’ must be replaced with ‘me’ to make the sentence grammatically correct.

Therefore, option A is the correct answer.