In the following sentence, should "is" be replaced with "are"?

Beowulf’s courage and willingness to fight to his death is what makes him a classic hero.

Yes, because of the plural subject.

Yes, "is" should be replaced with "are" in the sentence. Here's how you can figure it out on your own:

To determine whether to use "is" or "are," you need to identify the subject of the sentence. In this case, the subject is "Beowulf’s courage and willingness to fight to his death." Since the subject consists of multiple elements (courage and willingness), it is considered plural.

When the subject is plural, you use the helping verb "are" instead of "is." Therefore, the corrected sentence would be:

"Beowulf’s courage and willingness to fight to his death are what make him a classic hero."

By understanding the subject-verb agreement rule and identifying the subject in the sentence, you can determine which verb form is appropriate to use.