1.To some , happiness is being surrounded by family and friends.(L2)
1)主语+is doing sth.其中主语是物,该物能发出谓语动词所表示的动作,此处的doing 是动词的名词化。主语是人时,是进行时态。
eg. Her job is teaching English .(解释说明名词的性质或内容,表目前的情况,是一种静态) The teacher is teaching English .(正在进行的动作)
2)如表示将来要做的事情时,用:主语+is to be /do sth.