As is__________by scientists, global pollution has become one of the most serious problems humans are faced with.
A. predicts
B. predicting
C. predicted
Competition for these jobs is very tough---we have five times as many ________ this year as we did last year.
A. applicant
B. applicants
C. application
The car burns too much gas, and ________, the price is almost twice as much as I intend to pay.
A. moreover
B. however
C. whilst
To understand a great international event, we need to consider the _________background to it.
A. historical
B. history
C. historic