Problem: I can use this background: Naturally occurring uranium is composed almost entirely of two isotopes, uranium-238 (99%) and uranium-235 (1%). It is the uranium-235 that is fissionable (will undergo fission) and therefore, this is the uranium isotope than can be used for fuel in a nuclear reactor. For uranium to be used as fuel, the percent of uranium-235 must be increased to at least 3%. Uranium in which the U-235 content is more than 1% is called enriched uranium. Somehow, the two isotopes must be separated so that enriched uranium is available for use as fuel. Separating the isotope by chemical means (chemical reactions) is not successful because the isotopes have exactly the same chemistry. The only essential difference between U-238 and U-235 is their atomic masses; as a result, the two isotopes are separated by a physical means that takes advantage of the difference in mass. Now, I have a new situation: John is a nuclear scientist who works at the Fermi lab. Today, in front of him he has four samples, sample A, sample B, sample C, and sample D. Sample A is the naturally occurring uranium. Sample B is enriched uranium. Sample C is the U-238, and sample D is the U-235. He needs to figure out how to best use them. Answer this question please: Which sample would have lower percentage of uranium-235, sample A or sample B?

A: sample A

Problem: I can use this background: Millions of people in the world jog for exercise. For the most part, jogging can be a healthy way to stay fit. However, problems can also develop for those who jog in the heat. Excessive sweating can lead to electrolyte loss that could be life-threatening. Early symptoms of electrolyte deficiency can include nausea, fatugue, and dizziness. If not treated, individuals can experience muscle weakness and increased heart rate (which could lead to a heart attack). Many sports drinks can be consumed to restore electrolytes quickly in the body. Now, I have a new situation: Ted and Randy liked jogging. Last week while jogging by himself, Randy experienced an unpleasant episode and was taken to the hospital, because he passed out while jogging in the heat, without any water or supplements on him. Answer this question please: Which jogger experienced less dizziness?

A: Ted

Problem: I can use this background: There is worldwide concern about the relationship between climate change and the use of fossil fuels. Many scientists believe that increased use of these fuels (in vehicles and other gas-powered equipment) has the potential to irreversibly damage our environment. In addition to the environmental concerns, supplies of fossil fuels are finite, and because they are non-renewable energy sources, we will eventually need alternatives. New developments in batteries and other energy storage devices are being explored to help deal with these issues. Electrochemical processes are at the heart of these new technologies. Now, I have a new situation: Two countries used different fuels as power sources for their activities. Alsacia used fossil fuels, while Lorena devised more advanced energy storage devices, therefore relying on electricity. Answer this question please: Which country caused more environmental concerns?

A: Alsacia

Problem: I can use this background: As for the public health or food safety concern, organic foods are intended to be healthy, free of contaminations and free from agents that could cause human diseases. Organic milk is meant to have no chemical residues to consumers, and the restrictions on the use of antibiotics and chemicals in organic food production has the purpose to accomplish this goal. Although dairy cows in both organic and conventional farming practices can be exposed to pathogens, it has been shown that, because antibiotics are not permitted as a preventative measure in organic practices, there are far fewer antibiotic resistant pathogens on organic farms. This dramatically increases the efficacy of antibiotics when/if they are necessary. Now, I have a new situation: Manny and Annie were two foodie friends. Manny was a health conscious person, he ate organic foods and drank organic milk only. Annie liked all foods, whether they were organic or not. Answer this question please: Which friend drank more milk from cows treated with antibiotics?

A:
Annie