This group was made up of fierce fighters who would protect Georgia's southern border from invasion by the Spanish.

A. Highland Scots
B. Malcontents
C. Salzburgers
D. Trustees

A. Highland Scots

The correct answer is A. Highland Scots.

The correct answer is B. Malcontents.

To find the answer to this multiple-choice question, we need to examine the information provided and eliminate the incorrect options.

The question states that the group in question was responsible for protecting Georgia's southern border from invasion by the Spanish. Let's analyze each option and eliminate the ones that are not relevant:

A. Highland Scots: While the Highland Scots were an important group in the early colonization of Georgia, they were primarily focused on settling the northern regions of the colony and did not have a specific role in protecting the southern border from Spanish invasion.

B. Malcontents: The term "malcontents" refers to a group of settlers who were dissatisfied with the strict rule of the colony's trustees. While they did not have an official military role, they were known for their confrontational and rebellious attitude towards authority. However, they were not specifically tasked with protecting Georgia's southern border from Spanish invasion.

C. Salzburgers: The Salzburgers were a group of Protestant refugees from present-day Austria who settled in Georgia in the 1730s. They were primarily focused on religious freedom and establishing a cohesive community. They did not have a military function in protecting the southern border from Spanish invasion.

D. Trustees: The Trustees of the colony of Georgia were a group of British philanthropists who were granted a charter to establish and govern the colony. While they had overall responsibility for the colony's defense, they did not form a specific group of fierce fighters to protect the southern border from the Spanish.

Based on the above analysis, the correct answer is B. Malcontents, as they are the only option that does not get eliminated and can be associated with the specific task mentioned in the question.