Auxin and ethylene are the pair of enzymes that promote femaleness in flowers.

Explanation:
Flowering in plants is a highly coordinated process that involves the development of male and female reproductive structures within a flower. The development of female reproductive structures, including the pistil and ovule, is influenced by various plant hormones, including auxin and ethylene.

- **Auxin**: Auxin is a plant hormone that plays a crucial role in plant growth and development. In the context of flower development, auxin promotes the development of female reproductive structures. It helps in the growth and differentiation of the pistil, which is the female reproductive organ of the flower. Auxin also regulates the growth and development of the ovules, which are responsible for the production of female gametes.

- **Ethylene**: Ethylene is another plant hormone that regulates various aspects of plant growth and development, including flower development. In the context of femaleness in flowers, ethylene promotes the development of female floral organs. It enhances the growth and differentiation of the pistil and ovules, leading to the development of female reproductive structures.

The interaction between auxin and ethylene is crucial for the promotion of femaleness in flowers. Auxin acts as a positive regulator of ethylene biosynthesis, leading to an increase in ethylene production. This increased ethylene levels further enhance the actions of auxin, resulting in the development of female reproductive structures.

In contrast, other pairs of enzymes such as ethylene and cytokinins or auxin and abscisic acid do not specifically promote femaleness in flowers. Ethylene and cytokinins have roles in various aspects of plant growth and development, but they do not have a direct influence on the development of female reproductive structures. Similarly, auxin and abscisic acid have diverse roles in plant physiology, but they are not directly involved in promoting femaleness in flowers.

Therefore, the correct pair of enzymes that promotes femaleness in flowers is auxin and ethylene.