This is a______ but extremely difficult technology in the future.

_______ to catch the early train,but I didn’t get up in time. I have to stay here for another two days.

I will put the book________you placed it and make a mark at the place________I put it.

The plan we seems to be a big success.

It took us quite a long time to get to the amusement park. It was _______ journey. [ ]