A. Ionic, because electrons are shared
B. Covalent, because electrons are shared
C. Ionic, because electrons are transferred
D. Covalent, because electrons are transferred
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Nitrogen and oxygen are both nonmetals, which means they will share electrons in a covalent bond. For example, two oxygen atoms form a double bond, in which two pairs of electrons (four electrons total) are shared. Similarly, two nitrogen atoms form a molecule with a triple bond, in which three pairs of electrons (six electrons total) are shared.
Therefore, the Correct Answer is B.
Which example is part of the scientific method?
A. A student reads about a new way to harness energy from the sun.
B. A researcher studies the effects of car exhaust on how people breathe.
C. A researcher analyzes how many plants respond well to a new fertilizer
D. A student discovers how insulin plays a role in the development of diabetes
The Correct Answer is C.One step of the scientific method is to analyze information or data collected from the experiment to conclude whether the hypothesis is supported.
Recall that these make up the scientific method, described below:
What is the correct order of the stages of the cell cycle?
A. G1,S,G2,M
B. G2,S,G1,M
C. M,S,G2,G1
D. S,M,G1,G1
The Correct Answer is A.The cell cycle is an organized process divided into two phases: interphase and the M (mitotic) phase. During interphase, the cell grows and copies its DNA. After the cell reaches the M phase, division of the two new cells can occur. The G1, S, and G2 phases make up interphase.
It may appear that little is happening in the cell during the gap phases. Most of the activity occurs at the level of enzymes and macromolecules. The cell produces things like nucleotides for synthesizing new DNA strands, enzymes for copying the DNA, and tubulin proteins for building the mitotic spindle. During the S phase, the DNA in the cell doubles, but few other signs are obvious under the microscope. All the dramatic events that can be seen under a microscope occur during the M phase: the chromosomes move, and the cell splits into two new cells with identical nuclei.
Which choice best describes homeostasis?
A. A functional system of the body
B. Blood flow to every cell in the body
C. A relatively constant environment within the body
D. Neural pathways that have integrated into the body
The Correct Answer is C.Homeostasis is the existence and maintenance of a relatively constant environment within the body. Each cell of the body is surrounded by a small amount of fluid, and the normal functions of each cell depend on the maintenance of its fluid environment within a narrow range of conditions, including temperature, volume, and chemical content. These conditions are known as variables. For example, body temperature is a variable that can increase in a hot environment or decrease in a cold environment.
There are two types of feedback mechanisms in the human body: negative and positive.
The diffusion of nutrients through the walls of the digestive system is critical to homeostasis in the body. Where does the majority of this diffusion take place in the digestive system?
A. Stomach
B. Esophagus
C. Oral cavity
D. Small intestine
The Correct Answer is D.The duodenum is the first part of the small intestines, located between the stomach and the middle part of the small intestines (jejunum). Once food has mixed with acid in the stomach, it moves into the duodenum, where it then mixes with bile from the gallbladder and digestive juices secreted from the pancreas. In the duodenum, absorption of vitamins, minerals, and nutrients begins.
What solution has a pH of 7?
A. Aniline
B. Pyridine
C. Pure water
D. Sodium hydroxide
The Correct Answer is C.A pH of 7 is a neutral solution, which is how pure water is classified. Researchers can determine the strength of an acid or a base by measuring the pH of a solution. The pH value describes how acidic or basic a solution is. On pH scale, shown below, if the number is less than 7 the solution is acidic. A pH greater than 7 means the solution is basic. When the pH is exactly 7, the solution is neutral.