Chọn đáp án đúng: The farmer ______________ in the field when he saw a UFO6. The farmer ______________ in the field when he saw a UFO. A. is working B. was working C. worked D. works 7. A ______________ has a great view of the stars, so many scientists want to work on it. A. gravity B. cloud C. temperature D. space station 8. Scientists float in a space station because there’s no ______________. A. technology B. science C. gravity D. air 9. Jane’s mom: In 2100, there will be many space stations near Earth. Jane: ______________ A. Really? Why will you go there? B. What a good journey! C. I don’t know when they will come. D. Oh, it will be much easier to explore space. 10. The world’s ______________ is growing more quickly every year. Our planet is becoming more and more crowded. A. pollution B. popularity C. population D. pollutant 11. NASA is now working hard to ______________ whether there is life on Mars. A. discover B. collect C. experience D. accept 12. Humans can’t live unless they have enough ______________ to breathe. A. water B. planets C. food D. oxygen 13. Scientists have spent years ______________ information about UFOs. A. collecting B. to collect C. collected D. collect 14. Some scientists say that flying saucers might be people's ______________. A. imagination B. imagine C. imaginative D. imaginary 15. When you are in orbit, you'll be out of the earth's ______________ and you're weightless. A. outside B. gravity C. atmosphere D. outskirt |