Put the verbs in brackets in the past simple tense or past perfect tense.
1. Neil Armstrong and Buzz Aldrin (collect)________ some moon dust samples before they (return) _________ to Earth.
2. By the time Yang Liwei (become)________ the first person sent into space by the Chinese space program in 2003, NASA already (send) ________ over 100 people.
3. After the spaceship Soyuz 37 (be) __________ in orbit around the earth, Pham Tuan and Viktor Gorbatko (conduct)_________ some experiments.
4. When we (arrive)________ in Kennedy Space Center, the space shuttle already (launch) ________ into space.
5. Dennis Tito already (complete)_______ 900 hours of training by the time he (fly) ________into space in 2001.
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Sinh Học lớp 12
