In order to claim the demur right of advance performance, some conditions must be met. Which of the following is NOT a condition for claiming the demur right？
A. Both parties must owe obligations towards each other
B. There must be an order of performance
C. The party who claims this right must at first suspend its performance
提出“五官感觉的形成是以往全部世界历史的产物"这一主张的思想家是 ()
A. 康德
B. 黑格尔
C. 马克思
D. 恩格斯
Which of the following statements about the effect of a contract is correct？
A sales contract is subject to approval before it comes into effect
B. A contract becomes effective upon its formation, unless otherwise provided by law
C. The parties to a contract are not allowed to agree that its effect is subject to certain conditions
Under which of the following circumstances can an offer be withdrawn by the offeror？
A. The offer has not reached the offeree
B. The offer indicated a fixed time-limit for acceptance, which has passed
C. The offeree has replied to the offeror
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