Which of the following is NOT one of the conditions that must be met for a trade to be considered an arbitrage()

A. There is no risk. 

B. There are no commissions. 

C. There is no initial investment and there is a guaranteed profit.

急性炎症性脱髓鞘性多发性神经病病程的第三周，脑脊液改变最可能是

A．两性霉素B
B．氟康唑
C．5-氟胞嘧啶
D．泼尼松
E．吡哆醇