19. After discussion, we all think it’s an idea that’s worth _____.
Could it be in the room____ we had a talk last night ____ you left the key?
—I failed again. I wish I ____ harder.---But you ____.
While there are quite a few differences in the education system, in many countries education is ____.
Some plants are vey ____ to light; they prefer the shade.
—Can those ____ at the back of the classroom hear me?---No problem.