OTC market

which of the following statement regarding to OTC market is least accurate?
A. OTC market is less transparent and lightly regulated compare to auction market 
B. OTC market trade unlisted securities 
c. the trading volume of unlisted equities is much larger than the volume of debt
D. the contract in OTC market can be less standardized compare to auction market
老师您好，请问这道题为什么选C不是D？