What german monk believed that christians had to live by faith alone and depend on the mercy of god?

a.
john calvin

b.
martin luther

c.
leo x

d.
henry viii

 B. Martin Luther

Further detail ...

Here's an outline of Luther's life/career:

1483 - Luther was born in Eisleben, Germany1505 - Luther left law studies and entered the monastery.  There was a storm during which he vowed to become a monk if he survived the storm, but Luther had already been struggling over spiritual issues, doubting his soul's salvation.1512 - Luther earned his Doctor of Theology degree and became a faculty member of the University of Wittenberg.  His studies for teaching theology led him to his spiritual insights about grace in Christ.September, 1517 - Luther wrote "A Disputation against Scholastic Theology," a set of 97 theses aimed at the core teachings of the Roman Catholic church's main theological scholars.  This document didn't attract a lot of notice initially, because it was the sort of doctrinal debate university types would have with each other.October, 1517 - Luther wrote and posted "A Disputation on the Power of Indulgences," a set of 95 theses -- and commonly known simply as "The 95 Theses."  This document stirred up a firestorm, because it attacked the money-making asset that indulgences had become for the church.1518 - The Heidelberg Disputation.  Luther was called upon to defend his theology by his brothers in the Augustinian monastic order.  Luther's theses presented at Heidelberg were a defense of his teachings about Rome's "scholastic theology" (the September 1517 document).1521 - Luther was excommunicated by the pope.  At the Diet of Worms (a meeting of princes in the city of Worms), it was demanded that Luther recant his teachings.  He would not do so.  The prince who ruled Luther's territory, Frederick the Wise, whisked Luther away to the Wartburg Castle to keep him safe from harm.1522 - Luther's German translation of the New Testament (which he completed while at the Wartburg) was published.1524-25 - The Peasants' War occurred in Germany, as peasants revolted against nobles and landlords.  The peasants took Luther's reform movement against the church as a signal for changing society as a whole -- which was not something Luther himself supported.1525 - Luther published The Bondage of the Will, which he considered his most important work.  It was a response to Erasmus of Rotterdam who defended the freedom of the human will.  Luther pointed to the Bible and said our wills are enslaved in sin until God takes action to redeem us by his grace.  Notice that this is the same issue that Luther had been raising in his objections to "scholastic theology" in the Roman Catholic system.1530 - At the Diet of Augsburg, the newly forming Lutheran church was allowed to submit a confession of faith, which became known as the Augsburg Confession.  (Luther's colleague, Philip Melanchthon, wrote that confession.)1537 - Luther's own confession of faith, the Smalcald Articles, were prepared in case the Lutherans were allowed to present a confession at a council of the church that was being proposed.1546 - Luther died in Eisleben, Germany.  After Luther's death, wars of religion occurred between Roman Catholics and Protestants, including both Lutherans and Calvinists (who followed the teachings of John Calvin).  The Protestant groups could not be stamped out by force and became prominent in some parts of Europe.

What he said