. Probability is the mathematical study of the _____ of an event’s occurrence.

________, Henry studied even harder after he entered the university.

Though this kind of _______ has some _______, it is good enough for construction(建筑).

—What do you have for breakfast? —I often have ________ or ________. 

The drilling in Antarctica dragged on slowly because of lack of money, equipment breakdowns, environmental ______ and severe cold.