V. Put the verbs in brackets into the correct tense. 21. In 1962, John Glenn (become) _________________ the first American to orbit the Earthafter Yuri Gagarin (do) _________ it earlier before. 22. Russia (launch)___________the first space station called Salyut 1 before the United States (do)___________ the same with its first space station called Skylab in 1972. 23. Russian cosmonaut Alexei Leonov (walk)___________ in space before Neil Armstrong (become) ___________ the first man to walk onthe Moon in 1969. 24. In 1998, the International Space Station (ISS) (be launched)___________ into space after the United Statesand Russia (cooperate)___________in some projects. 25. The Mariner 9 (orbit)___________ Mars before Viking 1successfully (land) ___________ on the Red Planet.

21. In 1962, John Glenn (become) _______had became__________ the first American to orbit the Earthafter Yuri Gagarin (do) ____did_____ it earlier before.

22. Russia (launch)_____had lanched______the first space station called Salyut 1 before the United States (do)______did_____ the same with its first space station called Skylab in 1972.

23. Russian cosmonaut Alexei Leonov (walk)_____had walked______ in space before Neil Armstrong (become) _____became______ the first man to walk onthe Moon in 1969.

24. In 1998, the International Space Station (ISS) (be launched)_____was launched______ into space after the United Statesand Russia (cooperate)_____had cooperated______in some projects.

25. The Mariner 9 (orbit)______had orbitted(ko chắc nha)_____ Mars before Viking 1successfully (land) _______landed____ on the Red Planet.

V. 21. became-had done

22. had launched-did

23. had walked-became

24. was launched-had cooperated

25. had orbited-landed

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