Final answer:
The eldest son of Duncan in Shakespeare's play 'Macbeth', who nearly gets captured in the initial battle and flees to England afterwards, is Malcolm.
Step-by-step explanation:
In Shakespeare's play Macbeth, Duncan announces that he will name his eldest son, Malcolm, as the Prince of Cumberland. This is a significant moment, as Malcolm is not only established as Duncan's heir, but later in the play, after the murder of Duncan, Malcolm flees to England. The character you are asking about, Duncan's eldest son, who is almost captured in the battle at the beginning of the play and later flees to England, is Malcolm.
The other options in your question are not correct because Fleance is Banquo's son, Macduff is a thane of Scotland who plays a critical role in the play's conclusion, and Donalbain is Duncan's younger son who also flees after his father's murder, but to Ireland, not England. Therefore, the answer to your question is C) Malcolm.