How can you tell the difference between alternate and opposite leaf arrangements? They are based on based whether the leaf pinnate or palmate venation.
They are based on based whether the leaf has one or two leaves at the node.
They are based on based whether the leaf has a smooth or toothed margin.
They are based on whether the leaf is simple or compound.

They are based on based whether the leaf has one or two leaves at the node.

Explanation: You can tell the difference between alternate and opposite leaf arrangements based on whether the leaf has one or two leaves at the node. Alternate leaf arrangement is when a single leaf is attached at one location on the stem, the node, in an alternating pattern.  On the other hand, the opposite leaf arrangement is when two leaves are attached to the same node on opposite sides of the stem.  

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