The * is the one i think is right

1. An example of a geologic event that could be recorded in rocks is ____. (1 point)
a civil war
the occurrence of sun spots
a volcanic eruption *
a lunar eclipse
2. "The present is the key to the past." This statement rephrases the ____. (1 point)
principle of cross-cutting relationships
law of gravity
principle of uniformitarianism
principle of original horizontality *

5. An unconformity is a(n) ____. (1 point)
layer of sedimentary rocks
gap in the rock record
intrusion *
layer of rocks with unusual fossils
6. Which of the following environments would most likely NOT contain fossils? (1 point)
sediment deposited in a riverbed *
a thick deposit of dried mud
layers of sand that accumulate over thousands of years
intrusive rock formed from cooled magma
7. Why would a worm stand a poor chance of being fossilized? (1 point)
Worms did not exist in the geologic past.
Worms have been rare during the geologic past.
Worms have no hard parts. *
all of the above
8. Which of the following must be true for a fossil organism to be useful as an index fossil? (1 point)
The fossil organism must be widespread geographically.
The fossil organism must be abundant.
The fossil organism must be limited to a short span of geologic time.
all of the above *
9. Assume you began with 10 g of a radioactive parent isotope. How many grams of parent isotope will be present in the sample after 2 half-lives? (1 point)
5.0 g
2.5 g
1.25 g *
0.63 g

12. In living things, what is the source of the carbon-14 that is used in radiocarbon dating? (1 point)
carbon dioxide in rocks
carbonic acid in caves
carbon dioxide in the atmosphere
carbon dioxide in water *
13. Which of the following lists the divisions of the geologic time scale in order from longest to shortest? (1 point)
era, period, epoch *
epoch, period, era
era, epoch, period
period, era, epoch
14. Some continents contain large core areas of Precambrian rocks called ____. (1 point)
plates
rifts
plateaus *
shields
15. What is the major source of free oxygen in the atmosphere? (1 point)
molten rock
water
green plants *
silicate minerals
16. During the Pennsylvanian period, large tropical swamps extended across North America, eventually forming ____. (1 point)
vast coal deposits *
inland seas
tropical rain forests
mountain ranges
17. Why did amphibians diversify so rapidly during the late Paleozoic? (1 point)
They adapted to the cold climate.
They had little competition from other land dwellers. *
They were excellent hunters.
They could breathe underwater.
18. What were the first true terrestrial animals? (1 point)
reptiles
mammals
trilobites *
marsupials
19. The current geologic period is called the ____. (1 point)
Mesozoic
Tertiary
Quaternary *
Silurian

Note: your teacher will grade your responses to questions 21–22 to ensure you receive proper credit for your answers.
21. Can scientists use radiocarbon dating to find the age of a very tall, old redwood tree living in an old growth forest? Explain your answer. (2 points)

22. Describe how the meteorite collision at the end of the Mesozoic affected the atmosphere and the biosphere. (2 points)