( )是合同转让的实质。
A．合同权利义务的转让或转移B．合同权利义务的改变C．合同违约责任的改变D．合同标的改变
参考答案：A
有关牙内吸收的表述不对的是 （）
A.牙冠可呈粉红色
B.牙髓温度测验可正常
C.叩诊疼痛明显
D.X线片见髓腔内局限性不规则膨大透射影
E.正常牙髓组织变为肉芽组织
Transport by carrier proteins can be either active or passive, whereas transport by channel proteins is always passive. Explain your answer.
