找出下列句子的主语，并把主语填在横线上。
Lucy is a beautiful nurse.         _____________ 作主语
He reads newspapers everyday.    _____________ 作主语
Smoking is harmful to the health.   _____________ 作主语
To swim in Kunming Lake is a great pleasure. _____________ 作主语
What we should do is not yet finished.  _____________ 作主语