Q: The cycle of copper reacting is a good example of what principle? Read this paragraph and choose the correct option from the provided answers: A series of chemical reactions where an initial amount of copper reacts with nitric acid, goes into solution, and disappears. Then a series of reactions proceed, only to have the copper metal recovered. The copper cycle is a good illustration of how mass is conserved in a given chemical reaction. Choices: - law of inertia - conservation of energy - conservation of momentum - conservation of mass A:
conservation of mass

Q: What is the purpose of utilizing careful farming practices such as rotating crops or planting nutrient rich crops? Read this paragraph and choose the correct option from the provided answers: Careful farming helps to keep up soil quality each season. One way is to plant different crops each year. Another is to alternate the crops planted in each row of the field. These techniques preserve and replenish soil nutrients. Planting nutrient rich cover crops helps the soil. Planting trees as windbreaks, plowing along contours of a field, or building terraces into steeper slopes all help to hold soil in place ( Figure below ). No-till or low-till farming disturbs the ground as little as possible during planting. Choices: - improve sediment quality - improve photosynthesis quality - improve soil texture - improve soil quality A:
improve soil quality

Q: Silencing genes through epigenetic mechanisms is commonly practiced on what type of uncontrolled cells? Read this paragraph and choose the correct option from the provided answers: Cancer and Epigenetic Alterations Silencing genes through epigenetic mechanisms is also very common in cancer cells. There are characteristic modifications to histone proteins and DNA that are associated with silenced genes. In cancer cells, the DNA in the promoter region of silenced genes is methylated on cytosine DNA residues in CpG islands. Histone proteins that surround that region lack the acetylation modification that is present when the genes are expressed in normal cells. This combination of DNA methylation and histone deacetylation (epigenetic modifications that lead to gene silencing) is commonly found in cancer. When these modifications occur, the gene present in that chromosomal region is silenced. Increasingly, scientists understand how epigenetic changes are altered in cancer. Because these changes are temporary and can be reversedfor example, by preventing the action of the histone deacetylase protein that removes acetyl groups, or by DNA methyl transferase enzymes that add methyl groups to cytosines in DNAit is possible to design new drugs and new therapies to take advantage of the reversible nature of these processes. Indeed, many researchers are testing how a silenced gene can be switched back on in a cancer cell to help re-establish normal growth patterns. Genes involved in the development of many other illnesses, ranging from allergies to inflammation to autism, are thought to be regulated by epigenetic mechanisms. As our knowledge of how genes are controlled deepens, new ways to treat diseases like cancer will emerge. Choices: - giving cells - neutral cells - innoculous cells - cancer cells A:
cancer cells

Q: Burning trees produces most of the same pollutants as burning what? Read this paragraph and choose the correct option from the provided answers: Millions of acres of forest have been cut and burned to make way for farming. Figure below shows an example. Burning trees produces most of the same pollutants as burning fossil fuels. Choices: - fossil compounds - carbon - coal fuels - fossil fuels A:
fossil fuels