I would have to go with ( A) on that one
In Sir Gawain and the Green Knight, the one who first accepts the Green Knight’s challenge was of course King Arthur. This was the case because he was the one who’s being mocked by the Knight. However, when Arthur gets the Knight’s axe, Sir Gawain said that he would take the challenge himself.
The subordinate clause is "you must start researching now"
What book are u according to