A TCP/IP application receives files from a remote machine. The application reads 32 kilobytes of data at a time to the socket， but has not issued a system call to set the window size. Which of the following procedures should be performed on the personal machine to increase the throughput of the application？（）

A. Increase the size of thewall
B. Increase the size of sb_max
C. Increase the size of tcp_recvspace
D. Increase the size of tcp_sendspace