English Language · Grammar - Clauses and Phrases

Read the text and answer the question that follows: For decades, fusion has been described as the 'holy grail' of clean energy: abundant, virtually limitless, and without the long-lived radioactive waste that shadows fission. Recent advances—powerful magnets that confine plasma longer, lasers that trigger brief ignition—have revived optimism. Some experiments have achieved more energy out than in, at least momentarily. The excitement is genuine: a technology once consigned to 'always thirty years away' now seems to approach the horizon. Yet the path from ignition in a lab to electricity on a grid is treacherous. Scaling requires materials that withstand constant neutron bombardment, systems that run for months not microseconds, and financing that sustains multi-decade projects despite political cycles. Venture capital pours into startups promising compact reactors, while governments fund megaprojects that coordinate dozens of countries. Both pathways carry risk: the startup may overpromise, the consortium may delay under bureaucracy. Fusion's challenge is not only technical but civic. If progress is hyped too aggressively, the public may see setbacks as betrayal. If secrecy dominates, citizens may distrust an enterprise funded by their taxes. What endures is not slogans but credibility: publishing data, admitting limits, and testing claims openly. The prize of fusion is enormous, but the lesson of past technologies is clear—pace matters less than trust. What is the type of the underlined clause in the following sentence? Sentence: 'Startups promise compact reactors with rapid timelines that appeal to investors.'