What was one effect of the columbian exchange on the indigenous people

When the Europeans traveled to America, they brought with them diseases such as smallpox and malaria. Because the indigenous people had never been exposed to these diseases before, they had no immunity, and were therefore wiped out by the thousands. Over 90% of the Native American population was killed by foreign disease.

Idont know which one is right   but i know that c is wrong and a might be wrong