Choose the correct pronoun from the following five sentences:
"One" is correct. The sentence starts out using the third person pronoun, "one," so it needs to maintain that point of view throughout. Note that if you could change both of the pronouns in the sentence to the second person point of view, "you," that would be correct as well.
"When one sings in the choir, one should always control the volume so that no particular voice overwhelms the others."
"He" is correct. William Dean Howells is a man; you need to use the masculine singular pronoun "he."
"Although William Dean Howells was a famous author in the late nineteenth century, he is not very well known, or even heard of, today."
"He or she discovers" is correct. "A writer" is singular-- one writer. The singular pronouns are "he or she." To agree with a singular noun or pronoun, the verb usually ends in 's'.
"When a writer writes from personal experience, he or she discovers a great deal to say."
"It" is correct here, since there's one elephant and we don't necessarily know its sex.
"Peanut was the most unusual elephant; it had such large ears."
The repetition of the word "she" indicates that there is just one person involved here, so "she" needs to be maintained throughout the sentence in order to have pronoun agreement in number. If other sentences indicated that there were other people traveling with the woman, then, in certain cases, "they" could be correct.
"She knew that she was lost when she took that last left turn."