When two singular nouns joined by ‘and’ refer to two different persons and each preceded by an article, the pronoun used for them should also be plural.

Therefore, ‘himself’ must be replaced with ‘themselves’ to make a grammatically correct sentence.

Hence, option C is the correct answer.

We use the nominative case to show the subject of a verb. Remember that the subject is the noun or pronoun that performs the action of the verb.

‘She’ is the subject of the verb ‘is’.

Therefore, ‘she’ must be used instead of ‘her’.

Hence, option D is the correct answer.

We use the nominative case to show the subject of a verb. Remember that the subject is the noun or pronoun that performs the action of the verb. However, a pronoun used as the subject of an infinitive is in the objective case.

Therefore, the correct pronoun here is ‘me’, because it is the subject of the infinitive ‘to attend’. ‘I’ should be replaced with ‘me’ to form a grammatically correct sentence.

Hence, option B is the correct answer.

We use the objective case to show that the noun or pronoun receives the action. Here, ‘us’ is the object of the preposition for.

Therefore, ‘we’ must be replaced with ‘us’ to make the sentence grammatically correct.

Hence, option B is the correct answer.

A pronoun used in apposition with a noun is in the same case as the noun. An appositive is a noun or pronoun placed after another noun or pronoun to identify, explain, or rename it.

The pronoun must be in the nominative case (he) because it is in apposition with the noun engineers, which is in the nominative case.

Therefore, ‘him’ must be replaced with ‘he’ to form a grammatically correct sentence.

Hence, option B is the correct answer.

We use the possessive case to show ownership. Therefore, ‘her’ must be replaced with ‘hers’ to make the sentence grammatically correct.

Hence, option A is the correct answer.

We require pronoun in the object case. ‘They’ is a subject pronoun, and ‘them’ is an object pronoun.

Therefore, ‘them’ must be used instead of ‘they’ to form a grammatically correct sentence.

Hence, option D is the correct answer.

An apostrophe is never used in ‘its’, ‘yours’ and ‘theirs’.

Therefore, ‘their’s’ must be replaced with ‘theirs’ to form a grammatically correct sentence.

Hence, option C is the correct answer.

That’ must be used after determiners like all, same, any, none, nothing, only, everything, little, much and none.

Therefore, ‘which’ must be replaced with ‘that’ to form a grammatically correct sentence.

Hence, option B is the correct answer.

‘Who’ is used in the nominative cases while ‘whom’ is used in the objective cases.

Therefore, ‘who’ must be replaced with ‘whom’ to form a grammatically correct sentence.

Hence, option B is the correct answer.