Given a text T, and several options, according to the question posed in the text T to choose the most appropriate option from the options as the answer, please directly output the most appropriate option, do not need to output the explanation.

The Standard & Poor’s Depositary Receipts (SPDRs) is an investment that tracks the S&P 500 stock market index. Purchases and sales of SPDRs during an average trading day are best described as:
Option A:primary market transactions in a pooled investment.
Option B:secondary market transactions in a pooled investment.
Option C:secondary market transactions in an actively managed investment.

Answer: B