26. It is difficult to do some of the experiments ________ in our physics textbooks.
At the opening ceremony, the chairman ______ a speech to welcome the guests from more than twenty centuries.
Happy birthday, Alice? So you have _______ twenty-one already?
The conventional viewthat the Mars’ atmosphere is very poor because the planet lacks a magnetic field.
―Is that Miss Liu having dinner over there? ―Itbe her. She has gone to New York for an important business meeting.
We are working on the _assumption__________that everyone _________ will turn up.