【明報專訊】Esper smashed into a planet. "Hello, is anyone here?" he called. "Goodbye, go away!" a voice said. "I would if I could but I can't," Esper answered back. "Don't answer back to me!" the voice shouted. Esper was confused. He knew that answer back means to speak back to someone, but he didn't know it can also describe criticising or objecting to someone's orders!