"Engaging in aerobic activity three times each week will reduce cholesterol levels" is a:
A) substantiated explanation.
B) testable hypothesis.
C) scientific control.
D) critical experiment.
E) null hypothesis.
B) testable hypothesis
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Binary fission is:
A. cell division by meiosis B. cell division by mitosis C. cell division by simple splitting D. fluorescent in situ hybridization (FISH) E. exchange of genes between two cells
F-actin filaments
A) are composed of four linear strands. B) are composed of polymerized G-actin monomers wound around each other in a helix. C) are oriented similar to DNA, with strands helical and antiparallel to one another. D) are composed of G-actin dimers. E) polymerize at the same rate in both directions from both ends of the filament.
An electron microscope must use electromagnet 'lenses'shaped like donuts to direct the electrons onto the specimen. Why aren't they solid, like the lenses in a light microscope?
A. A magnetic field cannot be applied across a completely solid object-there must be an opening within the object for the field to be applied through. B. The user has to be able to physically look through the magnets to focus the beam of electrons onto the specimen, since the metal of the magnets is opaque. Without a hole in the middle, the user wouldn't be able to see! C. The electrons would destroy the electromagnet material unless there was a physical hole for them to travel through on their way to the specimen. D. Electrons are particles, and particles cannot travel through a solid item. The hole in the middle allows them to travel from the source of the electrons to the specimen.
Carbon, in the form of carbon dioxide (CO2), enters the atmosphere in several ways. Which of the following is NOT a process by which carbon dioxide enters the atmosphere?
A) cellular respiration of plants B) transpiration by plants C) respiration by oxygen-breathing animals D) burning of fossil fuels, such as coal and oil