presentation开头用1.First, we're going to .2.I'd like to begin by outlining our present situation.3.You may not know that .中间用Let's take a look at some of the implications of this.Taking into consideration what we have said about X, we can see that Y .The main reason for these actions is .We have to keep in mind that . when we consider .As you can see from this graph representing .If you could just take a look at .Looking at X we can see that There are a number of alternatives in this case. We can .If we had . , we would .Had we . , we could have . Do we need to X or Y?I think we can clearly see that we can either . or .We have been considering .结尾用We've discussed many points today. Let me quickly summarize the principal points:I'd like to quickly go over the main points of today's topic:Before we end, let me briefly recap what we have discussed here today.