The correct answer is: A. great
The other options are: B. huge, C. colossal, and D. abundant.
- Great means “very large or impressive in size, amount, or degree.”
- Huge means “extremely large.”
- Colossal means “extremely large or impressive.”
- Abundant means “existing or available in large quantities.”
In the context of the sentence, “I was astounded at his great lack of knowledge about the continent of Africa,” the word “great” is used to describe the extent of the person’s lack of knowledge. The person’s lack of knowledge is so great that it is surprising and even shocking.
The other options are not as appropriate in this context. The word “huge” could be used to describe the size of Africa, but it is not as appropriate to use it to describe the extent of someone’s lack of knowledge. The words “colossal” and “abundant” are not appropriate in this context at all.