Final answer:
The sentence 'I wondered why the baseball was getting bigger. Then it hit me' means that the baseball seemed bigger because it was approaching the speaker, and also that the speaker had a sudden realization (an 'aha moment').
Step-by-step explanation:
The two different meanings of the sentence "I wondered why the baseball was getting bigger. Then it hit me" are that B) the baseball was approaching quickly and C) the speaker gained insight. The first part of the sentence can be misinterpreted as the baseball physically increasing in size, which is not what is happening. Instead, the baseball appears to be getting bigger because it is coming closer to the speaker. The phrase "Then it hit me" is a play on words, serving both as a physical description of what literally happened and as a figurative way to describe the speaker's realization of why the baseball seemed to be growing larger.