Final answer:
The leaf arrangement that appears opposite due to leaflets attached to a midrib vein is called pinnately compound, and it is a characteristic of certain plants like roses.c) Opposite
Step-by-step explanation:
The type of leaf arrangement observed when leaflets are attached to a midrib vein, giving the appearance of an opposite arrangement, is actually a pinnately compound arrangement. Although at first glance they may seem opposite, because the leaflets are connected along the midrib, it does not qualify as a true opposite arrangement, which would require the whole leaves themselves to be directly across from each other on the stem. The pinnately compound leaf, with leaflets stemming from the central vein, is characteristic of plants like roses and hickory trees.