Explain the reason that the atomic emission spectrum of hydrogen contains only four lines. A)
The hydrogen atoms form a continuous series of quantized energy levels
that transmute at a variety of frequencies.
B)
Hydrogen atoms contain a limited number of quantized energy levels that
emit radiation at a limited number of frequencies.
C)
Many hydrogen atoms accomodate an array of quantized energy levels that
can release energy at a progression of frequencies.
A hydrogen atom consists of a sequence of quantized energy levels that
incorporate radiation only from consecutive frequencies.
D)

Often on a topographic map, every fifth contour line is darkened. what is this line called? a. key b. slope c. benchmark d. index contour

Look at the bean data from days 4–6. use these data to explain how natural selection changed the number of dark red walking beans over time. writing part

Quickly! brainliest if two people answer! 1. the blood has red blood cells, white blood cells and platelets. red blood cells carry oxygen to other cells in the body. cells need oxygen to live. white blood cells destroy certain germs. they protect our bodies from disease. which question is answered in this paragraph? (a) what is the role of blood vessels? (b) what type of cells are attached to bones? (c) what type of blood cell to clot your blood? (d) what are the different types of blood cells? 2. which sentence from the section "stem cells" best explains the role of stem cells? (a) when one kind of cell stops working, stem cells can . (b) they can turn into that cell and take its place. (c) scientists are studying new ways to use stem cells. (d) these cells can people heal faster. 3. read the selection from the section "nerve cells." nerve cells send messages to the rest of our bodies. these messages move between the brain, spinal cord and various organs. nerve cells are also called neurons. fill in the blank. a "neuron" is a (a) cell that moves information from the brain to other parts of the body (b) stem cell that has both an axon and a dendrite (c) cell that controls the fingers of a body (d) cell that makes up the spinal cord 4. some muscles in our body move without us telling them to. these are called involuntary muscles. some examples are the cardiac muscle cells inside the heart. these cells the heart relax and fill with blood. what is the best definition of "involuntary" based on the context clues? (a) something that happens on its own (b) trying hard to do something (c) something moving back and forth (d) easily moved