In winter, it is dangerous to go to school with snow ______the ground.

With so many people ______ in the mine(矿), none of the rescue workers would stop to have a rest.

 In the reading room, we found her seated at a desk, her attention ____ on a novel.

Most companies’ marketing effort is focused on getting customers, with little attention _______ to keeping them.

______ nobody else at hand, I had to carry the heavy box to the eighth floor by myself.