Which of the following statements are true for first-order analyses of nmr spectra (the type of analysis most commonly done).
a. the spin-multiplicity of the proton nmr absorption of the methylene group in ethanol-od is 4.
b. the difference in absorption frequency is equal to or less than 6 j.
c. carbon-13, an nmr-active nucleus, has a nuclear spin quantum number of 0.
d. first-order multiplets are symmetrical, and their chemical shift is given by the position of the first peak in the multiplet.
e. the peak multiplicity in a proton spectrum is (n+1), where n is the number of adjacent, equivalent hydrogens.