Final answer:
The relationship between increasing concentration of CO2 and the dry mass of velvetleaf is a positive correlation.
Step-by-step explanation:
The relationship between increasing concentration of CO2 and the dry mass of velvetleaf is a positive correlation. This means that as the concentration of CO2 increases, the dry mass of velvetleaf also increases, and vice versa. An example of a positive correlation in biology is the relationship between the amount of sunlight received by plants and their rate of photosynthesis.