Rutaceae is a disciflorae meaning ovary is superior and immersed in the disk of the flower. It shows Geraniales characteristic meaning ovule is pendulous. However, Malvaceae is thalamiflorae meaning sepals, petals and stamens are all attached to the receptacle. In Malvaceae, petals are separate, polypatalae. It has numerous stamens and valvate calyx. In Rutaceae, the calyx consists of 3-5 distinct or basally connate sepals and the corolla consists of 3-5 distinct petals. The androecium consists of distinct stamens that are commonly obdiplostemonous, that is in two whorls with the outer whorl opposite the petals.
Thus, the correct answer is option D.

The correct answer is option 'D', which states that Rutaceae differs from Malvaceae in having obdiplostemonous stamens. Let's understand the differences between these two families in detail:

Rutaceae:
1. Leaves: Rutaceae has simple leaves, which means each leaf is undivided and consists of a single leaf blade. The leaf blade may be entire or may have serrated margins.
2. Corolla: The corolla of Rutaceae is typically polypetalous, which means it consists of separate petals. Each petal is distinct and not fused with other petals.
3. Ovary: The ovary of Rutaceae is syncarpous, which means it is composed of multiple carpels fused together. The carpels may be partially or completely fused, forming a single ovary structure.
4. Stamens: Rutaceae has obdiplostemonous stamens. "Obdiplostemonous" refers to the arrangement of stamens in two whorls, with the outer whorl having one less stamen than the inner whorl. For example, if the inner whorl has 5 stamens, the outer whorl will have 4 stamens.

Malvaceae:
1. Leaves: Malvaceae also has simple leaves, similar to Rutaceae. The leaves are undivided and consist of a single leaf blade.
2. Corolla: The corolla of Malvaceae is also polypetalous, consisting of separate petals.
3. Ovary: The ovary of Malvaceae is superior, which means it is positioned above the attachment point of other floral parts, such as the sepals and petals. The superior ovary is not fused with the receptacle.
4. Stamens: Malvaceae has numerous stamens, which are usually monadelphous or diadelphous. "Monadelphous" refers to the stamens being fused together into a single group or column, while "diadelphous" refers to the stamens being fused into two groups.

In summary, Rutaceae and Malvaceae differ in terms of the arrangement of stamens. Rutaceae has obdiplostemonous stamens, while Malvaceae has stamens that are usually monadelphous or diadelphous.