They_____trouble lifting the heavy box.
. They are teachers and don't realize the basic/primary rules and principles _____ to start and run a company.
. The reason ________ he referred to for his success is ________ he always working hard.
. The teachers hope the little ________ has been learned will be useful when they leave school.
. “This is a window, ________ the sun comes in.” said the lady to her baby.
. Living in the western part of the country has its problems, ________ obtaining fresh water is not the least.