The correct option is (d) foetus
To explain I would say: The obstetrician is faced with the problem of having very few parameters available on which to base a diagnosis of foetal well-being or distress. In most cases, the condition of the foetus is assessed by studying the blood flow in the foetal heart and its heart rate. The foetal heart rate (FHR) yields important information about the status of the foetus, and therefore, has become a widely studied parameter in maternity cases.