In making a pizza, which process involves a chemical change?
===

baking the dough to form the crust

A geologist found fossils of horse bones in different rock layers of a canyon. The fossils in the lower levels show shorter bones than those in the upper-level fossils. Which conclusion is based on the geologist's observations?
===

Horse's became larger over time.

Which sentence best describes the organization of the heart?
===
The heart is an organ made up of different types of tissues, each of which has different types of cells.