What is the relationship between CHU and GDD regarding crop development?

The correct answer highlights that both CHU (Corn Heat Units) and GDD (Growing Degree Days) are temperature-based indices that help in assessing crop development. These indices utilize temperature data to estimate the growth stage of a crop, allowing farmers to predict when planting, growth, and maturity will occur.

CHU is specifically designed for corn, taking into account daily temperatures above a certain base temperature to determine the heat accumulation necessary for the plant's growth. Similarly, GDD is calculated using a base temperature to measure the cumulative heat exposure for a variety of crops. The relationship between these two indices is grounded in their joint reliance on temperature, which is a crucial factor in crop development.

The other options are not applicable because CHU and GDD do not serve as opposites or focus on factors such as humidity or frost effects. Their primary function revolves around temperature accumulation, making them indispensable tools for managing crop development effectively.