The sky is clouding over;we can see there ________ a rainstorm.
Mr. Green is said _____ an experiment to prove the new method of solving the problem when young.
—— Have you considered _____ your job as a teacher? ——Yes. I like the job because a teacher is often considered _____ a gardener.
The monument was built in honor of the explorer who was believed _____ the river.
You will see this product made in this factory _____ wherever you go.