A unifoliate compound leaf can be differentiated from simple leaf in having
A. Joint
B. Stalk
C. Unicostate reticulate venation
D. Multicostate reticulate venation

Hint: There is a completely subdivided blade in a compound leaf, with each blade leaflet split along a primary or secondary vein. The leaflets, the counterparts of the petioles and the stipules of the leaves, may have petioles and stipels.

Complete Answer:
There are two types of leaves: plain leaves and compound leaves. Compound leaves are further classified into leaves with pinnate compounds and leaves with palmate compounds.

Now, let us find the solution from the options-
- Option A: The leaflets emerge from a single point at the tip of the petiole in the palmate compound leaves. Based on the number of leaflets, it is further categorised into unifoliates, bifoliates, trifoliates, quadrifoliates and multifoliates. In a winged or a joint petiole, a unifoliate compound leaf may be distinguished from simple leaves. Thus, the option A is correct.
- Option B: The stalk that connects the leaf blade to stem is the petiole, which may rotate the leaf to face the light. This allows the plant a distinctive foliage arrangement. Thus, option B is not the correct option.
- Option C: Pinnate venation is often referred to as venation unicostatus. In this, a midrib or single principal vein is found in the lamina. Lateral veins are formed by it. Thus, option C is not the correct option.
- Option D: Multicostate venation is often referred to as palmate venation. There is more than one main vein in the lamina. Thus, option D is not the correct option.

Thus, the correct answer is option (A) Joint.

Note: Some families of taller plants, including the Fabaceae, are distinguished by compound leaves. A rachis is considered the middle vein of the compound leaf or perhaps a frond, when it is available.