Which of the following measures should be taken first in a neonatal resuscitation with no signs of meconium present?
a. Ensure an open airway by gently stimulating the baby and clearing any mucous or fluid from the mouth and nose
b. Begin positive pressure ventilation using a bag-mask device
c. Assess the baby's heart rate and initiate chest compressions if necessary
d. Administer oxygen if the baby is not breathing or has a low heart rate