会议期间的文书工作主要包括文件的分发和清退工作。
参考答案：错
已知x+y=6，xy=-3，则x2y+xy2=（ ）。
Attempts have been made for nearly three decades to increase the amount of precipitation from clouds by seeding them with salt or silver iodide.
A．Devices
B．Hypotheses
C．Efforts
D．Suggestions
