Choose the word (A, B, C or D) that best fits the blank space in the following passage.

One of the (13) _______ things that can happen on our earth is an earthquake. When earthquakes take place near large cities, many people may be killed and many buildings are (14) _______ down. Fire may start and (15) _______ more damage than the quake itself. Earthquake comes (16) ______ a shaking of the rocks under the surface of the earth. Forces within the earth push against the rocks until they break. We cannot tell exactly (17) _______ an earthquake is coming, but we can know places on the (18) _______ where they happen most often.

Điền vào số 17