One of the most common reasons why houseplants stop growing is simply a lack of nutrients. It may seem obvious, but one of the most common reasons why your plant might have stopped growing is because it's not getting enough of what it needs to thrive. i HOPE THIS HELPS
The "Introduction" section of a research article contains the detailed background information on the topic and the problem that is being answered by the research.
Experimental design as well as materials and methods are mentioned in the "Materials and Methods" section of a research article.
C. The question is hinting at the similarities between how single cellular organisms maintain homeostasis by regulating water levels the same way the kidney does for multi cellular humans.
