16.維生素A與三氯化銻的呈色反應(yīng)，其生成物的顏色為

A.藍(lán)色                                                          B.紫紅色

C.藍(lán)色漸變成紫紅色                                     D.黃色

17.在甾體骨架中，環(huán)戊烷屬于

A.A環(huán)                                                           B.B環(huán)

C.C環(huán)                                                           D.D環(huán)

18.可用硫色素反應(yīng)堿性鑒別的藥物是

A.維生素A                                                    B.維生素B₁

C.維生素C                                                    D.維生素D

19.鑒別黃體酮靈敏，專屬而又簡便的試劑是

A.間二硝基苯                                                B.異煙肼

C.亞硝基鐵氰化鈉                                         D.硝酸銀

20.青霉素分子中最不穩(wěn)定的結(jié)構(gòu)為

A.酰胺基                                                       B.β-內(nèi)酰胺環(huán)

C.羧基                                                          D.芐基