Nobody knows __ people began to use fire

Nobody knows how people began to use fire,does he? People began to use fire millions of years ago.对划线部分提问 people began to use mobile phones(phone) from then on. some people use fire to burn rubbish 保持句意不变 some people use 3个英语阅读题【一】Fire is important to us.People use fire to cook,to Nowadays people use fire not only to cook food but also to m It was a long time before people began to use written langua more and more people began to use mobile phones(mobile phone nobody knows what to do ,反义疑问句 nobody knows what is to happen next nobody knows Nobody knows.