Please answer the following question: Fact 1: The number of rings in a tree trunk can be used to estimate the age of the tree. Fact 2: Tree rings are examined to learn the forest age and growth rate. Given the two facts above, answer the question "you can determine the growth rate of the forest by examining what?" with the following options: - seasons - tissue - bark color - cycles - alleles - radiation level - rings - color gradient
A:
rings