The correct answer is: a) Life expectancy at birth.
Life expectancy at birth is a key indicator used to measure the health dimension of the Human Development Index (HDI). It is a measure of the average number of years that a newborn is expected to live if current mortality rates continue to apply.
The HDI is a composite index of three dimensions: life expectancy, education, and per capita income. It is used to rank countries by their level of human development. The HDI was developed by the United Nations Development Programme (UNDP) in 1990.
The HDI is a valuable tool for measuring and comparing the level of human development in different countries. It can be used to track progress over time and to identify areas where there is need for improvement.
The HDI has been criticized for being too simplistic and for not taking into account a wide range of factors that affect human development. However, it remains a widely used and respected index.
The other options are also important indicators of health, but they are not as widely used as life expectancy at birth.
Infant mortality rate is the number of deaths of infants under one year of age per 1,000 live births. It is a measure of the risk of dying in infancy.
Maternal mortality rate is the number of deaths of women due to pregnancy or childbirth per 100,000 live births. It is a measure of the risk of dying during pregnancy or childbirth.
Access to healthcare is the ability of people to obtain the health services they need. It is a measure of the availability and affordability of healthcare services.