Ionizing radiation, benzene, and certain viruses can each individually cause leukemia without the other two exposures, but only if the exposed individual has a certain genetic deficiency. This genetic deficiency by itself does not cause leukemia, but the disease never occurs in the absence of this genetic factor. The genetic deficiency is

A necessary but not sufficient cause

Explanation:

A necessary but not sufficient cause is defined as any cause/condition that is an obligate requirement for a particular event to occur (in this case, the particular event is leukemia disease), but it isn't sufficient for the occurrence of this event. Conversely, a sufficient cause is defined as any cause/condition that will cause by itself the event to occur. Finally, a condition is neither necessary nor sufficient when the condition neither is required nor sufficient for the event to occur.

a warm, wet climate will produce the highest rate of weathering. the warmer a climate is, the more types of vegetation it will have and the greater the rate of biological weathering (figure below). this happens because plants and bacteria grow and multiply faster in warmer temperatures.

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