You shouldn't leave the water ________ while you wash clothes; it's a waste of water.
92. The international police has come into existence and they were ____ the key to global security.
91. She likes to keep things rather than throw them ____ .
90. ____ the work was very difficult, they managed to finish it in time.
89. The task is hard, ____, the workers managed to finish it in time.
88. My old school friend comes to see me now and then. The underlined part means ____.