$(a)$ Label the three tiers $1, 2, 3$ given in the above age pyramid.
$(b)$ What type of population growth is represented by the above age pyramid?

(N/A) Based on the provided age pyramid:
$1$. Pre-reproductive population (the base tier,which is the widest,indicating a large number of young individuals).
$2$. Reproductive population (the middle tier).
$3$. Post-reproductive population (the top tier).
$(b)$ The age pyramid represents an expanding or growing population. This is characterized by a broad base,which indicates that the number of pre-reproductive individuals is significantly higher than the reproductive and post-reproductive individuals,leading to future population growth.