Combine each pair of sentence to make a complete sentence using a relative pronoun. Here is an example. A spacecraft is a vehicle. It is used for travel into space. → A spacecraft is a vehicle which is used for travel into space. 31. The International Space Station is a large spacecraft. It was launched in 1988. → _____________________________________________________________ 32. An astronomer is a scientist. An astronomer studies the sun, the moon and other planets. → _____________________________________________________________ 33. A telescope is a piece of equipment. Astronomers use it to observe stars. → _____________________________________________________________ 34. The place has a microgravity environment. Astronauts live and conduct research here. → _____________________________________________________________ 35. Space tourism is becoming more and more popular. It is space travel for recreational purposes. → _____________________________________________________________