It is only with the help of scientific research _____ bring PM1 air pollution under control.

We hurried there only ________ a note pinned on the door, ________ us the delay of the meeting.[ ]

We can never forget the days _______the two astronautsin spaceship worked together and the days _______we spent together.

If you had seen a doctor, you much better now.[ ]

the 5,000 year old “Iceman”,______on the alpine border between Italy and Austria in 1991