1.some of the fossils that have been found from before the cambrian explosion are embryos this suggests that the organisms these fossils belong to
a. have bilateral symmetry
b. reproduce asexually
c. exhibit cephalization
d. reproduce sexually
2. most of the body features found in invertebrates evolved during which of the following periods?
a. Jurassic
b. Cambrian
c. cretaceous
d. Permian
3. a marine biologist exploring a deep sea trench locates a new species of soft bodied creatures with an unfamiliar shape. he is able to determine that the creature is a mollusk because it has
a. bilateral symmetry
b. body segmentation
c. an internal shell
d. am internal skeleton

The formation of an embryo (zygote) is a characteristic of sexual reproduction since it occurs as a result of the union of a female gamete with a male gamete.
The Cambrian is the period in which most groups of animals appear in the fossil record. The animals that characterize the Cambrian fauna are basically groups of invertebrates such as annelids, arthropods, porifers and echinoderms.
Of the described options, the only characteristic of mollusks is bilateral symmetry, since they are not segmented and are soft-bodied animals, ie, they don't have internal skeletons or shells.