You are a professional level SQL Server 2005 database administrator in an international corporation named Wiikigo. You are experienced in implementing high-availability solutions， monitoring the database server， and design deployment. In the company， you major job is the deployment， maintenance and support of Microsoft SQL Server 2005. You work as a database administrator for your company. The users report the slow performance of a SQL Server 2005 application. You are required to identify the queries which perform slowly because of blocking. Which action should you perform？（）

A. In a SQL Trace log file， you should look for queries with low duration values and high read and write values.
B. In a query execution plan， you should look for queries with missing or out-of-date statistics.
C. In a SQL Trace log file， you should look for queries with high duration values and low read and write values.
D. In a query execution plan， you should look for queries with a large number of table scans.