When a source emits sound energy, sound waves spread out over an ever-enlarging sphere, decreasing in intensity as they travel. Also, some sound energy is absorbed by the air (or other medium) along the way. Which of the following do these phenomena best help to explain?

The amount of dissolved gas in a liquid solution depends on the pressure of the gas. Under a high pressure, greater amounts of gas can be dissolved. Pressure is used to increase the solubility of carbon dioxide gas in

The DNA of every human includes two sex chromosomes, which determine gender and the traits associated with gender. Female sex chromosomes are both of type X, while a male has one X chromosome and one Y chromosome.
How is the gender of human offspring determined?

Which chart depicts the evolutionary relationship between the hummingbirds and flowers described?
Certain types of red-colored flowers produce nectar that is chemically ideal as food for a hummingbird. The hummingbird can easily locate these flowers because it can see the color red especially well. The recurved petals of these flowers remain out of the hummingbird’s way while it extracts nectar with its long beak that is perfectly suited for the task. As it does so, the hummingbird’s head feathers brush against the flowers, collecting pollen that it carries away and disperses.

In the early 19th century, almost all peppered moths collected by biologists in the U.K. were pale and mottled. Only rarely was a collector able to find a dark-peppered moth. After the Industrial Revolution, when furnaces filled the air with dark soot, the light-peppered moth became rare and the dark-peppered moth was most common in industrial cities. A reasonable explanation for this change is that the dark moth was less likely to be seen and eaten by birds against the dark background. This explanation illustrates the principle of

Most animals have internal or external skeletons for structure and support. Which of the following parts provide a similar function in plant cells?

Hemoglobin in the blood carries from the respiratory organs (lungs or gills) to the rest of the body (i.e. the tissues):

Deficiency of which of the following leads to dental caries?

Homeostasis is a state of equilibrium. Every living thing tries to achieve homeostasis by regulating its processes. To achieve homeostasis, a cell that has taken in food would also need to do which of the following?

All of the following are primates EXCEPT

In an exothermic process, heat is released by the process to the surroundings. An example of an exothermic process is burning wood. An endothermic process requires the input of heat from the surroundings. An example of an endothermic process is boiling water.Which of the following is an endothermic process?

From where does the sun derive its energy?

Which of the following is the first artificial satellite launched from earth?

A neutral object is rubbed with a material such that it becomes positively-charged. What must have happened?

Which of the following could be the most effective solution of getting relief from a bee-sting?

In addition to magnifying the image of an object, a microscope inverts the image left to right. The image of the object observed through the microscope is also upside down. Looking through the eyepiece, you would therefore see the upside-down mirror image of the object under the microscope lens.What would the object below look like if observed through the microscope?

A decomposition reaction will involve the:

Which of the following function is not performed by bone?

Which of the following is not true?

Farmers could have a good yield of rice for a fairly long time without adding any nitrogenous manure because