2 The bell ________ the end of the period rang, interrupting our heated discussion.A indicating B indicated C indicates D to indicate
Many students today suffer from ________ problems, since they are under too much pressure.
________ energy is generated from natural resources—such as sunlight, wind, rain, tides and so on.
Effective measures have been taken to prevent _______pollution.
It worried her a bit ____ her hair was turning grey.
_______you come or not is up to you.