[单项选择]

Earthquakes may rightly be ranked as one of the mo

st destructive forces known to man: Since records began to be written down, it has been estimated that earthquake-related fatalities have numbered in the millions, and that earthquake-related .destruction has been beyond calculation. The greater part of such damage and loss of life has been due to collapse of buildings and the effects of rockslides, floods, fire, disease, tsunamis(gigantic sea waves), and other observable events resulting from earthquakes, rather than from the quakes themselves.
The great majority of all earthquakes occur in two specific geographic areas. One such area covers the Pacific Ocean and its bordering landmasses. The other extends from the East Indians to the Atlas Mountains, including the Himalayas, Iran, Turkey, and the Alpine regions. It is in these two great belts or zones that ninety percent of all earthquakes take place; they may, however, happen anywhere at any time.
This element of the un
A. may happen anywhere at any time
B. are hardly the direct cause of fatalities
C. are unobservable in masses of land
D. mostly strike in oceans and mountains