We can get the energy we require for our everyday needs from many sources, but not all of them are ________.  

Fish and poultry have a much lower impact ____ the environment, and other plant proteins are even less damaging ______ the planet.  

You should use electric fans rather than air conditioners _________ they don't emit dangerous gases. 

E-books are typically __________ through a student's personal device, such as a notebook, tablet or cellphone. 

Choose the best one (A, B, C or D) to complete each of the following sentences. 

She can't get home _________ she has no money.  

Mr. Brown has created a list of the most useful apps for the classroom, _________ is available on his blog.