Q: In humans, a trait can be determined by one pair or many pairs of OPTIONS:
- genes
- microbes
- cells
- organs
A: genes
The items listed below were found in a science classroom. * a heart made of plastic with many of its parts labeled * clay formed to look like Earth and other planets * a giant plastic plant cell with removable cell parts These items are all examples of
OPTIONS:
- models
- experiments
- variables
- controls

models
Q: In addition to oxygen, which gases make up the largest percentage of Earth's atmosphere? ---- OPTIONS:
- hydrogen, helium, and water vapor
- hydrogen, methane, and ozone
- carbon dioxide, water vapor, and nitrogen
- carbon dioxide, methane, and helium

A: carbon dioxide, water vapor, and nitrogen
Hydrochloric acid is added to a beaker containing a piece of zinc. As a result, zinc chloride is formed and hydrogen gas is released. This is an example of
===
OPTIONS:
- a chemical reaction
- a physical change
- photosynthesis
- evaporation

a chemical reaction
Question:
The surface of Earth is constantly changing. Which of these findings provides the best evidence that the crustal surface of Earth has changed over time?
OPTIONS:
- Some rock layers are very thick.
- Some species have become extinct.
- Marine fossils are found in mountain areas.
- Igneous rock is found on all tectonic plates.
Answer:
Marine fossils are found in mountain areas.
*Question*: Which statement describes animal embryos? OPTIONS:
- display all the features of an adult
- represent the earliest stage of development
- have the same number of cells as a fertilized egg
- have half the number of chromosomes as an adult
*Answer*:
represent the earliest stage of development