Professor Zhang’s new theory is excellent.—That’s right. But I fear that is something you will not find easy to _____ to the audience.

By the time he realizes he________into a trap, it’ll be too late for him to do anything about it.[ ]

It really seemed ages _____ the police came on the scene and cleared away the damaged cars [ ]

John shut everybody out of the kitchen ______ he could prepare his grand surprise for the party.[ ]

依次填入下列横线处的词语，最恰当的一组是（ ）研究伊始，该团队选取了华北、西北地区生产的几十种马铃薯进行分析 ，从营养成分、 硬度等方面多次试验， 确定了适合加工马铃薯面条的两个品种。随后，又从诸多面粉种类中试验选取了 的小麦粉加以调试。