No one has yet succeeded in explaining the ___ of how life began.

China has got a good ________ for fighting against the flu with its careful and smooth organization.

Putin will run for president next March in an election that could open the way for him to stay in ______ for 12 more years.

Students sometimes support themselves by ______ of part time job.

Health problems are closely connected with bad eating habits and a _____ of exercise.