A low birth rate most likely indicates that there is a strong health-care system in place. This is because effective health care can contribute to family planning and access to reproductive health services, leading to fewer births.
To break down the other options:
- A high death rate typically correlates with a low birth rate but is not a direct indication of it.
- A long life expectancy can often relate to lower birth rates, but it doesn't directly indicate the birth rate itself.
- High fertility would contradict the idea of a low birth rate.
In conclusion, among the provided options, the one that best aligns with the implications of a low birth rate is "There is a strong health-care system in place."