A student observed the melting point of 4-methoxychalcone to be 63-70oC. Which of the following is (are) plausible explanation for this observation? Answer A. product was pure. B. product has small amount of side products. C. product was not dried completely before taking the melting point. D. product was very cold when the student started taking the melting point. E. product was not recrystallized successfully.