What scientific field studies the geographic distribution of plants?

The correct choice is phytogeography, as it specifically focuses on the geographic distribution of plant species and the factors that influence this distribution. It examines how various environmental factors such as climate, soil type, and geographical barriers shape where different plant communities thrive. Phytogeography looks at patterns of plant distribution on a regional and global scale, investigating historical processes that have led to current patterns in vegetation.

In contrast, ecology is a broader discipline that studies the interactions between organisms and their environment, encompassing not just plants, but also animals, microorganisms, and the ecosystems they inhabit. While ecology may touch on aspects of plant distribution, it does not focus exclusively on plants.

Botany is the scientific study of plants, including their physiology, structure, genetics, ecology, distribution, and taxonomy, but it does not specifically concentrate on geographical distribution alone.

Biogeography studies the distribution of all living organisms, including animals, plants, and microorganisms across geographic areas and through geological time. While it includes the distribution of plants, it is a more encompassing field than phytogeography. Therefore, phytogeography is the most precise term for the study in question, making it the correct choice.