Answer:
B. We were walking by the lake when we heard a siren.
C. By the time I graduated, I had attended three different high schools.
D. Though he had been rude at first, Rupert eventually won over the congregation
Step-by-step explanation:
Verbal tenses indicate when the action, state or phenomenon expressed by the verb occurs. When a change of verbal tense occurs within the sentence, it is necessary that this change does not interrupt the relation of coherence and cohesion of the text, because this will leave the phrases meaningless and will not allow the understanding of the reader. For this reason, the letters B, C and D are those that present an acceptable change in verbal tense, because the change maintains the coherence and cohesion of the sentence.