1.It is a great pleasure for me to have this wonderful chance to speak here.
　　2.What I want to stress is that protecting the environment is of vital importance.
　　3.I am speaking to you as a representative of the students who have graduated from this school this year./ I have the honor to speak on behalf of the students who have graduated from this school. (我代表毕业生讲话)
　　4.No one can deny the fact that the environment is playing an important role in our life.
　　5.Thanks for your listening to my speech.