In this task, you are given a question and an answer, you would be asked to create the sentence based on the Question-Answer provided. It should be contained within the Question-Answer provided.

Question: What is the key to the demographic transition? Answer: reduced family size
Reduced family size is the key to the demographic transition.

Question: What develops in depressions where water flow is low or nonexistent? Answer: bogs
Bogs develops in depressions where water flow is low or nonexistent.

Question: What system do trees need to transport nutrients? Answer: vascular

Trees need the vascular to transport nutrients.