Answer:
A. A pairs with U
Explanation:
In DNA, the nitrogenous bases are A, T, G, and C. In RNA, the nitrogenous bases are A, U, G, and C.
A pairs with U in RNA because it requires less energy to use uracil over thymine.
Hope that helps.
<span>Levels of OrganizationIn unicellular (single-celled) organisms,
the single cell performs all life functions. It functions independently.
However, multicellular (many celled) organisms have various levels of
organization within them. Individual cells may perform specific
functions and also work together for the good of the entire organism.
The cells become dependent on one another.Multicellular organisms have
the following 5 levels of organization ranging from simplest to most
complex:<span><span>LEVEL 1 - Cells<span><span>Are the basic unit of structure and function in living things.
</span>May serve a specific function within the organismExamples- blood cells, nerve cells, bone cells, etc.</span></span><span>LEVEL 2 - Tissues<span>Made up of cells that are similar in structure and function and which work together to perform a specific activity
Examples - blood, nervous, bone, etc. Humans have 4 basic tissues: connective, epithelial, muscle, and nerve.</span></span><span>LEVEL 3 - OrgansMade up of tissues that work together to perform a specific activityExamples - heart, brain, skin, etc.</span><span>LEVEL4 - Organ Systems
<span>Groups of two or more tissues that work together to perform a specific function for the organism.
Examples - circulatory system, nervous system, skeletal system, etc.
The
Human body has 11 organ systems - circulatory, digestive, endocrine,
excretory (urinary), immune(lymphatic), integumentary, muscular,
nervous, reproductive, respiratory, and skeletal.</span></span><span>
LEVEL 5 - Organisms
<span>
Entire
living things that can carry out all basic life processes. Meaning they
can take in materials, release energy from food, release wastes, grow,
respond to the environment, and reproduce.
<span>Usually made up of organ systems, but an organism may be made up of only one cell such as bacteria or protist.
</span>Examples - bacteria, amoeba, mushroom, sunflower, human</span></span></span></span>
The place in your body is called the Lungs.
