Last summer I took a course on ________ poisonous gases.[ ]

Mr Hu has travelled to six countries _______.

Things like eye contact and hand gestures _____ great importance in situations such as job interviews．

The wireless video camera is ________to send its video signal to a nearby base station，allowing it to be viewed on a computer or a television

As for sports, I like baseball better than tennis. How about you— For me, I prefer ________.