The possible weather system of low pressure trough is () A. Cold front B. Warm front.

Cold and warm fronts can form a cover cyclone in the trough of low pressure, but not in the ridge of high pressure.

Principle: First, the cold front goes down and the warm wind goes up.

When they meet, there will be a shift. However, in the trough with low pressure, the atmospheric height is low, and there is not enough space to open the gap and let the cold and warm fronts pass, so there will be frontal cyclones. On the contrary, in the ridge of high pressure, the atmosphere is high, and there is enough space to widen the gap and let the cold and warm fronts pass, so naturally no frontal cyclone can be created.