In recent years, in the research process of drug analysis and identification methodology, the multi-functional technical characteristics of nmr have been fully reflected and expanded, forming the trend of "diversification" of detection techniques. do you know what aspects "diversification" is reflected in?

① There are many test methods: many kinds of NMR test methods, including one-dimensional and two-dimensional, have been widely used in structural analysis and material identification; quantitative analysis is no longer limited to 1H NMR experiment, and quantitative analysis of heteronuclear and even two-dimensional NMR appears frequently;

② There are many calibration targets: most compounds have multiple sets of NMR lines, which can be used as calibration targets for quantitative analysis theoretically, which undoubtedly provides convenience for the processing of test data;

③ There are many types of quantitative information: in the literature reports, not only the integral area or intensity of the resonance spectral line is used as the data parameter of NMR quantitative analysis, but also the change value of chemical displacement under specific conditions can be used as the parameter of content determination;

④ There are many reference modes: nuclear magnetic resonance obtains the data information of quantitative analysis through direct comparison of signals. In the experiment, multiple modes such as internal standard, external standard, solvent calibration and physical calibration can be used to provide reference signals. In the determination of relative content, the mode of sample self-standard can also be used.

In a word, NMR is a mature analytical and testing method with distinct technical characteristics, multiple means, flexible methods and rich information, which has a strong competitiveness in drug analysis and identification.

Explanation:

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chert is a sedimentary rock composed of microcrystalline or cryptocrystalline silica. with this little bit of information, you can come to the conclusion that your answer is c.  

explanation: