Read the sentence.

after we heard the way he played the song on his guitar, we bought it.

which analysis correctly identifies the pronoun error and solution?

the pronoun “we” should be changed to “us.”
the pronoun “he” should be changed to “they.”
the pronoun “his” should be changed to “himself.”
the pronoun “it” should be changed to “the song.”

The pronoun "it" should be changed to "the song"

Explanation: The last option is the only one which solves the ambiguity of the pronoun "it," whose antecedent in this sentence was not clearly defined and could have been "the guitar" or "the song." All the other options lead to invalid sentences: "we" is always a subject, not an object in this sentence (so it can't be changed to "us"), replacing "he" with "they" would break coherence with "his guitar" and the possessive pronoun "his" would lose its function if changed to the reflexive pronoun "himself".

he will find out what went wrong or happened and how.

active voice: my father cut the tree.

passive voice: the tree was cut by my father.

active voice: people buy newspapers every day.

passive voice: newspapers are bought (by people) every day.

active voice: people have been using movies as political propaganda since world war ii.

passive voice: movies have been used as political propaganda since world war ii.

active voice: donna gave me my birthday present.

passive voice: i was given my birthday present (by donna). / my birthday present was given to me (by donna).

active voice: mom will leave the keys on the counter.

passive voice: the keys will be left (by mom) on the counter.

the words in parentheses are the agent of the passive voice and can be omitted when obvious, generic, or simply unnecessary.