Water molecules enter cells by which of the following transport mechanisms?

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 A. This option describes a chemical reaction known as the reaction of water with sodium, producing hydrogen gas. Chemical reactions involve the breaking and forming of chemical bonds, and in this case, sodium reacts with water to produce hydrogen gas and sodium hydroxide.

The correct answer is C. 9. The pH is determined by taking the negative logarithm (base 10) of the hydrogen ion concentration ([H+]). In this case, -log(10^(-9)) equals 9, so the pH of the solution is 9.

To find the pH of a solution with a hydrogen ion concentration ([H+]) of \(10^{-9}\) M using the equation \(pH = -\log[H^+]\):

\[ pH = -\log(10^{-9}) \]

Now, since \( \log(10^{-9}) = -9 \), the negative sign before the logarithm makes the value positive:

\[ pH = -(-9) = 9 \]

Therefore, the solution has a pH of 9

The correct answer is D. The hip joint allows for a wide range of motion and is characterized by a ball-and-socket structure, where the rounded head of the femur fits into the cup-like socket of the acetabulum in the pelvis. This type of joint permits movement in multiple directions.

The correct answer is D. The typical pathway of blood flow involves arteries branching into arterioles, which further branch into capillaries, facilitating the exchange of nutrients and gases with the organ's tissues.

The correct answer is B. Gray matter in the brain primarily consists of neuron cell bodies, dendrites, and unmyelinated axons. It is involved in information processing and integration.

The correct answer is C. The digestive system is responsible for breaking down complex food molecules, including proteins, into simpler components such as amino acids that can be absorbed and utilized by the body.

The pharynx is primarily composed of muscle tissue. It plays a role in swallowing and is part of both the respiratory and digestive systems, which requires coordinated muscular activity.

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 B. Objects A and B have the same mass, but B falls faster because it has less air resistance. Objects C and D have different masses, but C falls faster because it has a higher mass-to-surface-area ratio, which reduces the effect of air resistance.