19. Answer B. Scientists can infer theage of fossils found in rock strataby counting thetimerequired to deposit the layers above the layer in which the fossils are found.

20. Answer C. Sometimesfoldingcan overturn strata, so that older layers lie on top of older ones. The folds are bends in rock layers caused by intense pressure within the earth.

21. Answer A. Afaultis a break in the earth’s crust along which there is movement. It can be seen that layers B, C, D, and E are shifted along this line, while layer A was deposited after the fault occurred.

22. Answer D. Layer E represents in igneous intrusion. This intrusion must have occurred after layers B, C and D were formed making layer Eyounger than layers B, C, and D. The movement of layer E with the other layers indicates it occurred before the fault.

23. Answer A. Extrusions and intrusions are the result of molten magma, which when cooled, crystalizes to formigneous rock.

24. Answer B. The rock was formed in layer D first, it is the lowest. This was followed by layer C, then by layer B, one on top of the other. Layer E is an intrusion that happened after D, C and B were formed. Layer A was deposited last, on top of all the others. This makes layer D the oldest, corresponding togranitein the key.

25. Answer C. The correct answer ishypertonic solutions have a lower concentration of water than the cell, while hypotonic solutions have a higher concentration of water than the cell.The comparison of solutions to one another is not correct, because the hyper and hypo labels apply to how the solution relates to a cell, not another solution.

26. Answer C. Kayro syrupis the hypertonic solution. This is the solution that causes a decrease in the egg’smassbecause the water moving from the egg (cell) to the outside solution.

27. Answer B. The isotonic situation isvinegar to salt water.Thedata tableshows that there is no change in themassof the egg. Thatmeanswater has neither left or entered the egg. The solutions have the same tonicity.

28. Answer A. The egg immersed in syrup.We are told that plasmolysis occurs in hypertonic solutions, and the syrup solution is the hypertonic solution among those tested.

29. Answer A. We can infer thatthe concentration of solute in the ocean is higher than that in the solution tested.The passage tells us that the ocean is a hypertonic solution, and the way the salt water in ourexperimentbehaved showed that it was hypotonic. This must be the result of differing solute concentrations.

30. Answer B. Thetemperatureand volume of a gas are inversely related.Thisexperimentis designed to investigate the relationship betweentemperatureand volume, not pressure.

31. Answer A. 108 mLThe volume predicted by Charles’s Law should make the two ratios 140/373 and V/288 equal.

32. Answer A. Incompletely clamping the rubber tubing after boiling.Incompletely clamping the rubber tubing would allow the hot gas to escape and, potentially, be replaced by cooler gas.

33. Answer D. Air must be allowed to escape the bottle; otherwise the pressure inside the bottle would be higher than atmospheric pressure.Theexperimentrelies on the pressure of hot and cold air being identical. Plus, heating a trapped gas in a glass container isn’t safe.

34. Answers D. Weighing the water in the bottle, instead of pouring it into agraduated cylinder.Some water will never end up in thegraduated cylinder. Weighing the water will eliminate this problem.

35. Answer C. 19 mLThe decrease intemperatureof 15oC between Part 1 and Part 2 produced an increase of 8 mL. Dropping another 20°C should produce a similar drop.

36. Answer D. presence of nucleic acid.Like bacteria, dormant viruses contain one of two nucleic acids, DNA or RNA.

37. Answer B. Researches determined that viruses consisted of a nucleic acid, but the scientific view of line changed: viruses may becomplex biochemical mechanisms, but not alive.

38. Answer B. An important characteristic of life is theresponse to stimuli.Viruses may exist in two distinct states. When not in contact with a host cell, the virus remains entirely dormant. When the virus comes into contact with the appropriate host, it becomes active and directs all efforts toward self-replication.

39. Answer B. There would be more support for viewpoint #1 if viruseshad a cellular rather than particle structure, as noted in viewpoint #2. Virusesdocommandeer host cells in order to synthesis proteins and reproduce.

40. Answer B. Scientists first hypothesized that viruses were a simple life form because, like bacteria,they were known to cause disease.