人人都知道股市波涛汹涌、风云变幻，但有些人还是幻想能赚到股市中的最后一分钱。股海淘金，我们需要仔细权衡投资的 [ ]

A．股票价格、预期股息、银行利息税

B．价值尺度、流通手段、贮藏手段

C．安全性、收益率、流通性

D．信用度、保障范围、赔付标准

Which of the following condition is least likely to be the reason that a black market is generally inefficient（）

A. Unenforceable contract.

B. Increased prices required by suppliers due to the risk of prosecution.

C. Intensive control by the government.