Our government should ____ stricter measures to make sure all food products meet the quality standards.

-------Do you have enough to ________all your daily expenses? --------Oh yes, enough and to spare.  

As civilization______, more and more people have realized the importance of preserving rare animals from extinction.

Noone has _____ been able to trace the author of the poem.

The police are trying to find out the ____ of the woman killed in the traffic accident．