The key to exercise solutions in chapter 7c - Grammar in use for the textbook On Screen B2+ - Student's Book with authors Virginia Evans and Jenny Dooley from Express Publishing
Question
Join the sentences using the words in brackets.
Answer
Although many people have studied them, the purpose of the Nazca Lines is unexplained.
Christa McAuliffe was part of the Challenger crew despite not being a trained astronaut.
We went to Egypt in order to see the pyramids.
Our professor talks as if he believes aliens really exist.
The mission to Mars was cancelled due to insufficient funds.
The purpose of Stonehenge is such a complex mystery that no one has been able to solve it.