The coastal city is ______ in natural resources, especially sea foods and water resources. 

At times the balance in nature is ______，resulting in a number of possibly unforeseen effects.

It is ___________ that this matter hasn’t been paid attention to.

—What do you plan to do on the ___________ May Day holiday?—I have no idea. Probably, I will spend it by doing many papers.

I knocked at the door hard,and soon the door opened and a _____ face looked out, “ who is troubling me at this time of night.”