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the ultimate source of energy flowing into nearly all ecosystem is: A. wind B sunlight C electricity D.geothermal vents E. radioactivity
A consumer eating a producer represents :A a transfer of chemical nutrients and energy B a transfer of chemical nutrients but not a transfer of energy C. a transfer of energy but not a transfer of chemical nutrients D.none of above
3.Which of is (are) properties of life? A a complex organization B the ability to take in energy and use it.C.Thr ability to respond to stimuli from the environment D. The ability to reproduce
E. all of them are correct
4. Which id correct? A genes are proteins that produce DNA.Beach organism has its own unique DNA code. C.DNA relies upon 5 different building blocks as the alphabet if inheritance. D.Differences among organisms reflect different nucleotide in their DNA E. Each DNA molecule is a single strand of nucleotides.
5.Which one is false? Living systems A must have two or more cells B.Maintain a relatively consistent internal environment. C.responds to changes in the environment D.Encode their genetic information in DNA. E.Grow and develop
6. the 4 most common elements in living organisms are : A.. c,h,o,fe. B. c,h,o,na, C. c, n,o,na, D.fe, n, o, ca. 留学生作业代写
7. The nucleus of an atom contains: A. protons and neutrons. B. protons and electrons. C. only neutrons. D. only protons. E. only electrons.
8. A(n)_____ forms when two atoms share electrons. A. ion B. element. C.covalent bond. D.ionic bond E.hydrogen bond.
9. The oxygen atom of a water molecule. A.is more positively charged than the hydrogen atoms. B. attracts electrons less strongly than the hydrogen atoms. C. is more electronegative than the hydrogen atoms. D is electrically neutral. E is attracted to the negatively charged atoms of other molecules.
10. _____are weak bonds that are not strong enough to hold atoms together to form molecules but are strong enough to form bridges between molecules.
A. ionic bonds B. covalent bonds. C.polar covalent bonds. D. hydrogen bonds. E. non-polar covalent bonds.
11. A solute is: A. the dissolving agent of a solution. B. The liquid portion of a solution. C. Usually water in living cells. D. the substance that is dissolved in a solution. E. the dissolving agent of a solution that is usually oxygen in living cells.
12. Bases.: A. donate H+ ions to solutions. B. Accept H+ ions from solutions .C.Donate OH- ions from solution. D. Accept OH- ions from solutions. E. either accept H ions from solutions or donate OH- ions to solutions.
13. A solution with a ph7 is: A. strongly acidic. B. Stongly basic. C. weakly basic. D. Neutral. E. Weakly acidic.
14.which of the following statements about ph is/are true.: A.The ph scale is a measure of oxygen ion concentration. B. A single unit change in the Ph scale is equivalent to 1% change in hydrogen ion concentration. C. an increase in hydrogen ion concentration means a decrease in PH scale units. D. Basic PH levels are less than 7. E. the ph of solutions inside most cells is close to 9.0
15. In the equation 2 H2 +O2—2H2O, the H2 molecules are__and the H2O molecules are__: A.Reactants..products. B.Products…reactants. C.Reactants…reactants. D.Products…products. E.None of the choices are correct.留学生作业代写
16. which of the following is not a characteristic of chemical reactions? A.Chemical reactions involve the making and breaking of chemical bonds. B. Some chemical reactions create electrons,