When a warm air mass moves between two cold air masses, it leads to the formation of clouds due to the rising and cooling of the warm air. This is mainly because the warm air becomes saturated with moisture. Therefore, clouds are the expected outcome in this situation. ;
When a warm air mass moves between two cold air masses, clouds are likely to form due to the rising and cooling of the warm air, which causes moisture to condense. Therefore, the correct answer is D. clouds form.
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