The "gray matter" of the brain is largely made up of which of the following?

The correct answer is B. The phenotypic ratio of 50% green pods and 50% yellow pods indicates that the genotype of the parent with green pods is heterozygous (Gg), and the genotype of the parent with yellow pods is homozygous recessive (gg). The cross would be Gg x gg.

The correct answer is D. The scientific purpose would be to analyze the factors that led to the failure of the 1924 expedition, providing insights into mountaineering challenges and safety considerations, rather than demonstrating modern technology or exploring new routes.

The correct answer is D. Mitochondria are the cellular organelles responsible for the production of ATP (adenosine triphosphate) through the process of cellular respiration.

The correct answer is A. Increasing the surface area of a solid reactant by grinding it to a powder exposes more particles to the reactants, enhancing their chances of colliding and increasing the reaction rate. The other options would generally decrease the rate of the reaction.

The correct answer is B. Uracil is a nitrogenous base found in RNA, replacing thymine which is found in DNA. Adenine, guanine, and cytosine are common to both RNA and DNA.

The correct answer is B. Parathyroid hormone (PTH) regulates blood calcium levels by stimulating the release of calcium from bones, reabsorption of calcium in the kidneys, and absorption of calcium in the intestines. Norepinephrine, growth hormone, and melatonin do not play a primary role in calcium regulation.

The correct answer is C. Psoriasis is a chronic autoimmune skin condition characterized by the rapid buildup of skin cells, and it is considered a noninfectious disease. Chikungunya, dengue, and brucellosis are infectious diseases caused by specific pathogens.

The correct answer is C. Helper T-cells play a crucial role in the immune system by coordinating and stimulating other immune cells, including cytotoxic T-cells, to attack and destroy foreign agents.

The correct answer is A. Browning of an apple is often caused by enzymes such as polyphenol oxidase. Lemon juice has a low pH, creating an acidic environment that inhibits the activity of these enzymes and prevents browning.

The correct answer is B. Emphysema is a disease that primarily affects the alveoli, which are tiny air sacs in the lungs responsible for gas exchange. The destruction of alveoli walls in emphysema reduces the surface area available for oxygen and carbon dioxide exchange.