问题如下：
An investment that tracks the S&P 500 stock market index is the Standard & Poor’s Depositary Receipts (SPDRs). Which of the following statements is correct?
选项：
A. Purchases and sales of SPDRs during an average trading day are best described as primary market transactions in a pooled investment.
B. Purchases and sales of SPDRs during an average trading day are best described as secondary market transactions in a pooled investment.
C. Purchases and sales of SPDRs during an average trading day are best described as secondary market transactions in an actively managed investment.
解释：
B is correct.
SPDRs is a pooled investment vehicle and trading in the secondary market.
请问c为什么不对呢？