Passage Summary: Scientists claimed that for an antenna to work perfectly across all frequencies, it needs a specific shape. They built one with that shape, but it didn't work perfectly across all frequencies. Because of this, an expert says their original rule about the shape must be wrong.

Conclusion: The researchers' claim that an antenna must be symmetrical and fractal to work equally well at all frequencies is incorrect.

Reasoning: The researchers created a new antenna that is both symmetrical and fractal, yet it performs better at lower frequencies than at higher ones.

Analysis: The expert's logic is a textbook example of confusing a necessary condition with a sufficient one. The researchers stated that the shape is a requirement (necessary) for the performance, not that the shape alone guarantees (sufficient) that performance. If I say you must have a key to open a door, and you have a key but the door is also bolted from the inside, it doesn't mean my statement about the key was wrong. Look for an answer choice that identifies this failure to distinguish between what is required and what is enough to produce a result.