1. He observes keenly, but says little. 他观察敏锐，但言语寥寥。
2. She remained keenly interested in international affairs. 她一直对国际事务有强烈的兴趣。
3. They're keenly aware that whatever they decide will set a precedent. 他们敏锐地意识到无论他们决定怎么做，都会开创先例。
4. They had been longing to have each other to themselves, apart from the world, but it seemed they never felt so keenly that they were still units in modern society. 他们一直渴望与对方独处，远离世界，但似乎他们从未如此强烈地感到自己仍然是现代社会中的一员。
