For A.) When there is an injury, the blood platelets start to accumulate around the open wound to begin clotting and prevent bleeding.
Explanation: If you have a wound on the skin, then white blood cells immediately go to the wound to heal the wound, so that you don't bleed.
For B.) The blanket brain sends signals to reinforce the clotting process until blood loss from the injury is stopped completely.
Explanation: The brain helps send signals to the white blood cells to notify them to try to stop the bleeding.