产品的品质、品牌和商标、包装、式样等属于产品的层次中的（）
A.核心层
B.有形特征层
C.附加利益层
D.无形特征层
参考答案：B
The number of visitors_________ small today, but a number of visitors here yesterday. [ ]
A. is; were
B. are; was
C. is; is
D. are; are
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