Final answer:
The weakest research question is asking for the best flower for a specific type of garden without any research objective or hypothesis.
Step-by-step explanation:
The weakest research question out of the options provided is option C: What type of flower grows best in a Pacific Northwest garden?
This question does not involve a specific research objective or provide any hypothesis to test. It simply asks for information about the best flower for a specific type of garden, which is subjective and does not contribute new knowledge to the field.
On the other hand, the other options offer more focused research questions that can be explored through experimentation, data analysis, and scientific investigation.