Explanations:Relative clauses are used to provide additional information about a noun in a sentence. In this case, the sentence is "One of the persons teaching at the workshop yesterday was my sister." The task is to replace "teaching" with a relative clause that maintains the same meaning and grammatical structure.
The main clause of the sentence is "One of the persons was my sister," which is in the past tense. Therefore, the relative clause must also be in the past tense to maintain consistency. The correct relative clause is "who taught," as it is in the past tense and correctly modifies "persons" to provide information about the action that occurred in the past.
Let's examine the other options to understand why they are incorrect:
Option B, "She that taught," is incorrect because "that" is not typically used to refer to people in English. Instead, "who" is the appropriate relative pronoun for people. Additionally, the structure "She that taught" is not a valid relative clause construction.
Option C, "who is teaching," is incorrect because it is in the present tense. The main clause is in the past tense, so the relative clause should also be in the past tense to maintain consistency.
Option D, "She was teaching," is incorrect because it uses the past continuous tense. The past continuous tense is used to describe an ongoing action in the past, but in this context, the action of teaching is a completed action, so the past simple tense "taught" is more appropriate.
Option E, "who would teach," is incorrect because it uses the past future tense. This tense is used to describe a future action from a past perspective, but the sentence is describing a completed action in the past, so the past simple tense "taught" is the correct choice.
In summary, the correct relative clause is "who taught" because it is in the past tense and correctly modifies "persons" to provide information about the action that occurred in the past. This maintains the grammatical consistency of the sentence and accurately conveys the intended meaning.