Final answer:
The mammal subspecies that can reach 19 feet tall is the giraffe, which is suited for feeding on tall foliage in its habitat.
Step-by-step explanation:
The Masai subspecies of mammal that can reach 19 feet tall is the giraffe (A). Among ungulates (hoofed animals), giraffes are exceptional for their height. This characteristic enables them to feed on leaves from tall trees that other ground-dwelling animals cannot reach. In contrast, other land mammals like elephants, hippopotamuses, and rhinoceroses, tend to move more slowly and have different adaptations for their respective habitats. While elephants are large and have a significant presence in their habitats, they do not match the height of the giraffe. The same goes for rhinoceroses and hippopotamuses, which are adapted for different ecological niches. Thus, answer A) Giraffe is the correct choice, as this mammal is known for its towering height and long neck that contributes to its ability to reach high foliage for feeding.