Which of the following organisms are known to reproduce by budding?

Budding is a form of asexual reproduction where a new organism develops from an outgrowth or "bud" from the parent organism. This process allows the offspring to grow while still attached to the parent until it is mature enough to separate.

In the case of Hydra and yeast, both organisms utilize this form of reproduction. Hydra, a simple freshwater animal, can reproduce by producing buds on its body, which then develop into new individuals. Yeast, a type of fungus, also reproduces asexually through budding; a small bud forms on the parent cell and eventually detaches to become an independent yeast cell.

Other choices feature organisms that reproduce differently. Frogs and fish typically reproduce through sexual reproduction, laying eggs that will develop into embryos. Birds and mammals also reproduce sexually, with more complex reproductive systems that involve internal fertilization and live births in the case of most mammals. Trees and shrubs might reproduce through a variety of means, including sexual reproduction via seeds and asexual methods like vegetative propagation, but budding is not their primary means of reproduction.