6227 - Intermediate\Upper-Intermediate Test:4 - New sources of energy ______ developed. This will become increasingly important as oil reserves ______ up.

New sources of energy ______ developed. This will become
increasingly important as oil reserves ______ up.
has been / have been used
have been / is used
is being / are used
are being / are used
Table of English Grammar Contents (All Levels)
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