Step 1: Understanding the sentence.
The sentence is: "He was quite amusing when he heard what had happened." The error lies in part B ("was quite amusing").
Step 2: Analyzing the word choice.
- The word "amusing" is an adjective, which describes something that causes amusement. It is typically used when describing an object or an action, not a person's state or feeling.
- The word "amused" is the correct adjective to describe a person who feels pleasure or enjoyment from something, which fits the context of the sentence, as the person is reacting to hearing something.
Step 3: Correcting the sentence.
The correct sentence should read:
"He was quite amused when he heard what had happened."
This makes sense because the person (he) is feeling a certain way (amused) upon hearing the news, not causing amusement.
Step 4: Conclusion.
Therefore, the part of the sentence that is incorrect is B ("amusing"), and the correction should be to change it to "amused."