A、They prevent you from making great difference. B、They make great difference by minor details. C、They make little difference by

Today, I’d like to tell you how to be effective. I was in the gym one day, training like usual, when my coach made an important observation. We looked across the gym and saw someone performing lateral raises with dumbbells while standing on a Bosu ball.
    My coach watched for a moment and then said, "Imagine how good you have to be for that exercise to be the thing that gets you to the next level."
    His point was that this person was focusing on an exercise that improved a few, tiny muscles in their body while ignoring the more important foundational movements.
     (23)In other words, the problem is that too many people waste time on the details before mastering the fundamentals. And I’d say the same is true outside of the gym as well.
    Everybody has the same basic body and needs, and we have to have the courage to train the fundamentals, the basics, at least 80% of the time. Sure, add some spice in there now and again, but focus on the basics.
    Committing to the basics and mastering the fundamentals can be hard. And I get it. I’ve struggled to fall in love with boredom and focus on the basics many times.
    For example, as an entrepreneur it is very easy for me to spend my days working on the details. Should I make a small tweak to my website design? Should I answer these 50 emails? Should I switch my payment processor so that I can save an extra 2 percent on fees?
     (24)All of these things have a place, but that place should not be at the top of my to-do list. Instead, my time would be better spent focusing on the fundamentals. For example, writing two really good articles each week.
    In the words of my friend, Corbett Barr, people waste too much time debating edge cases.(25)Edge cases are the what-ifs, the could-bes, the minor details—the things that might make a 2 percent difference, but mostly distract you from the real work that would make 80 percent of the difference.
    Most people avoid the fundamentals because they don’t have the guts to become great at them. When you eliminate everything that is unnecessary, there are no details to hide behind. You’re left with just the basics and whether or not you have mastered them.
    It’s easier to tell people that you’re "working on a new strategy" or you’re "doing more research." It’s hard to say, "I’m focusing on the basics, but I haven’t made much progress yet."
    Hope you enjoy today’s lecture. Thanks for listening!
23. What does the speaker imply by his gym experience?
24. What does the speaker mention as his fundamental?
25. What do we know about edge cases?