Final answer:
The speaker's strongest piece of evidence was his personal example of the 100-day rejection challenge, which showed that rejection can lead to unexpected possibilities.
Step-by-step explanation:
The speaker's strongest piece of evidence to prove his claim is the personal example he shared about his 100-day rejection challenge. This is mentioned in the TED Talk video 'Jia Jiang: What I learned from 100 days of rejection' at approximately 4 minutes and 25 seconds into the talk
During this challenge, Jia Jiang deliberately sought out rejection for 100 days, asking for things like borrowing $100 from a stranger or requesting a 'burger refill' at a restaurant. By facing the fear of rejection head on, he discovered that rejection doesn't have to be a negative experience. In fact, it can open up unexpected possibilities and opportunities.