The traffic department has taken effective measures ________ the car speed in the town and ________ the traffic accidents.[ ]

Do you think I should wear a hat to theparty——It all depends on your own__________

Science is really _______ useful sucject although it is very difficult.

Friends are those__________ makeyou smile，alwaysopen their hearts to you and encourage you to succeed

My friend had ________really unusual experience last year.