Waves 2 and 4 typically show alternation between “flat” (sideways) type and “deep” (sharp) corrections. If wave 2 was “deep,” like a zigzag (most typically), then we can expect wave 4 to be a “flat” type of correction: triangle or flat.
Waves A and C will alternate most of the time as well. If A is a sharp move that is fast and silky smooth, almost one strong effort; then wave C is typically going to be more subdivided, like a channel or a diagonal (i.e. slower and wobbly, or even turbulent, that might grind as far or even further than A).