... birds, animals, fish which are not tame ______________ 2) keeping something from harm ______________ 3) the process of making something dirty or impure ______________ 4) barren area, desert ______________ ... lightning / thunder and then heard a deep boom. c) The traffic had to slow down because of the thick fog / vapour. d) There won’t be much rain. It’s only a short shower / stream. e) Spring ... them. d) It would be a good idea to _________ more trees, not to __________ trees. e) We can use things again if we __________ rather than ___________ them. Exercise 9: Choose the correct word...