His radio is a very old one. It sometimesworks and sometimes it_______

Modern China is experiencing a completely new period ________ respect for science and creativity has become the guiding principle of society.[ ]

He has been working so hard _____ he could answer such a difficult question[ ]

Progress so far has been very good._________ , we are sure that the project will becompleted on time.

Only by________your attention________what you are learning can you learn it well. [ ]