Answer: B
Step-by-step explanation:
The answer is, to start to develop, because, according to the definition, germinating means "to start to develop." In this sentence, the word germinating is used to describe the process of Zara's new ideas starting to develop in her mind. We know this becuse, the sentence says that she had been germinating the ideas over the last few days, which means that the ideas had been developing over time.