The correct answer is (b) St. Thomas.
St. Thomas was an apostle of Jesus Christ. According to tradition, he traveled to India after the resurrection of Jesus and preached the Gospel there. He is said to have been martyred in Mylapore, Chennai, India.
St. Paul was a Christian missionary who traveled extensively throughout the Roman Empire. He is considered one of the most important figures in the development of Christianity.
St. Augustine was a bishop and theologian who lived in the 4th and 5th centuries AD. He is considered one of the most important figures in the development of Western Christianity.
St. Francis was a 12th-century Italian friar who founded the Franciscan order. He is known for his simple lifestyle and his work with the poor.
St. Thomas is the most likely candidate for the title of “first Christian missionary to come to India” because there is historical evidence that he traveled to India and preached the Gospel there. The other three options are all important figures in Christianity, but there is no evidence that they traveled to India.