First question: a. Gastrulation Gastrulation is a phase<span> of the </span>embryonic development<span> in </span>animals. It doesn't occur in plants or any other organism. The other options can be put apart because <span>multicellularity, sexual reproduction, and </span>flagellated sperm are also characteristics that are present in plants, for example. Heterotrophic nutrition is something that's part of all <span>animals as well as non green plants.
Second question: a. M</span><span>ulticellularity </span>Synapomorphy is <span>a shared </span>trait <span>that distinguishes a </span>clade<span> from other organisms. C</span>hoanoflagellates are considered the most close ancestors to the animals distinguishing from them by multicellularity. They are very studied with the purpose to know the mechanisms of colonies' formation and evolution to multicellular animals.
Third question: <span>d. Choanoflagellates This are the most closely related living protist group. The </span>choanoflagellates are very similar to the ch<span>oanocytes of the sponges bringing them into closeness with the animals. They even aggregate in colonies, and are thought, because of all of this, to be the closest branch of single cells to that of the animals.</span>
