Answer: A) to provide information about how the characters should move or speak onstage.
Step-by-step explanation: Based on how the stage directions are used in the given excerpt from act I, scene I of Richard III, we can see that the main purpose of providing stage directions in a drama is to to provide information about how the characters should move or speak onstage, for example: "Alarum. Enter KING RICHARD III and RICHMOND; they fight. KING RICHARD III is slain. Retreat and flourish."