The companies are working together to create ______ they hope will be the best means of transport in the 21st century

______ difficulty, you can reach me at this number. I’m always at your service.

s Tu Youyou once commented, “In order to make some achievements and ______ yourself in your field, there are certain things you must do.”

_______ they stop to have a rest? —No, let them go on.

They ___________to put their hearts into study..