Teachers have to constantly update their knowledge in order to maintain their professional(专业的)_______.

We all agree that the products of this factory are of better ________.

 Those black clouds are a sure _____ that it’s going to rain. 

According to a UN report，one third of the world population have no    to clean drinking water and health care.

 Health officials have tried to raise _______ about the H1N1 flu among all people.