Final answer:
King Duncan awards Macbeth the title of Thane of Cawdor after the previous thane is executed for treason.
Step-by-step explanation:
In the play Macbeth by William Shakespeare, King Duncan asks Ross to give the title of Thane of Cawdor to Macbeth, as the current Thane of Cawdor has been executed for treason. Duncan believes that Macbeth deserves to inherit this title due to his valiant efforts in battle. This act of naming Macbeth the Thane of Cawdor fulfills part of the witches' prophecy and sets Macbeth on the path to kingship, which he contemplates deeply throughout the play.