A．The threats humans pose to Arctic seabirds,
B．The diminishing colonies for Arctic seabirds.
C．The harm Arctic seabirds may cause to humans.
D．The effects of the changing climate on Arctic seabirds.

A．It has decreased.
B．It has been exaggerated.
C．It has become better understood.
D．It has remained basically the same.

A．It develops more easily in centenarians not actively engaged.
B．It is now the second leading cause of death for centenarians.
C．It has had no effective cure so far.
D．It calls for more intensive research.