After walking on the zigzag path to the mountain top for a few hours, the tourists gathered under trees_____ shade and______ down to have a rest.

_________ the project as planned, we’ll have to work two more hours a day. 

I would love _______ to the party last night but I had to work extra hours to finish a report. 

      their final medical check, the astronauts boarded their spacecraft．

 English teachers are supposed ______their students a test in class, even after class, ______better teaching results.