Which sentence from the passage most strongly supports the author's overall purpose in writing?
a.
shepherds, farmers, and ranchers consider the ideal guard animal to be one that is effective, fearless, cost-effective, and easy to maintain.
b.
llamas are members of the south american camelidae family and are used as beasts of burden in many areas of the world.
c.
in a study conducted by iowa state university in 1990, llamas were rated as effective guard animals by 80 percent of sheep owners.
d.
a guard animal lives with a herd or flock to protect the livestock and deter predators.