The correct answer is B) blue color and lack of breathing. This is the correct answer because blue color (cyanosis) and lack of breathing are the clear signs of respiratory arrest, which requires immediate administration of artificial respiration. Unconsciousness (A) can be a sign of respiratory arrest, but it is not a direct sign in itself. Vomiting (C) and irregular breathing (D) may be associated with respiratory distress, but they are not definitive signs of complete respiratory arrest requiring artificial respiration. The key indication is the lack of breathing and resulting blue discoloration of the skin, which signals the urgent need for artificial ventilation.