It remains __________ whether this teaching method will be better than that one.
I don’t believe the reason ____ he has given for not coming to the lecture.
In the forest we observed some trees ____the leaves were black with disease.
I often think of the years ____ I worked with the foreigners, ____ has had a great effect on my later life.
He expressed his hope ____ he would visit China again the next year, and this was the very hope ____ he expressed as soon as he arrived in the country.
____ has finished the task ahead of time will be rewarded, though we don’t know who it will be.