Raoul ate a meal of oats before seeing his doctor. Oats are made of mostly starch molecules. Raoul feels tired, so his doctor gave him a test and found that Raoul’s cells contained glucose molecules, but they did not contain enough oxygen molecules. Does this explain why Raoul feels tired? A. No, something else must be wrong because his cells have all the molecules they need.

B. Yes, his digestive system is breaking down starch molecules, but his respiratory system may not be working properly.

C. Yes, his respiratory system is working, but his digestive system is not getting energy from combining glucose molecules.

D. Yes, his digestive system is working, but his respiratory system is not breaking down oxygen, so his body stopped making energy.

Scientist: cross-sections of stalactites—calcite formations deposited on cave ceilings by seeping water—can reveal annual variations in rainfall in particular areas over hundreds and thousands of years. we often found that when—according to these cross-sections—drought occurred in a particular area, it coincided with the collapse of an ancient society in that area. i hypothesize that drought reduced agricultural productivity in these areas, thereby leaving these societies without the resources needed to handle internal stresses and external threats. which of the following, if true, would most weaken the support for the scientist's hypothesis? a. many droughts indicated in the cross-sections of stalactites do not correspond with the collapse of a society in that area. b. information from the cross-sections of stalactites alone cannot reveal the level of agricultural output in an area at a particular time. c. most of the societies that collapsed during droughts did so when internal power struggles coincided with military raids from neighboring societies. d. most of the societies that collapsed during droughts maintained large stockpiles of food and water at the time of their collapse. e. information from stalactites also suggests that the collapse of some societies coincided with periods of abnormally high rainfall.