The work was difficult, but Tom’s          expression showed that he would finish it in time.

-- I’m very tired these days because of studying for physics.--Why not    music? It can make you    .

Once out of the earth’s gravity, the astronaut is________ by the problem of weightlessness.

With April 18’s railway speedup,highway and air transport will have to compete with_______service for passengers.

His father was really a ______ person. Once he made up his mind, nothing could change it.