胎儿时期经升主动脉的血液不供应的器官为()
A．上肢
B．脑
C．心脏
D．下半身
E．上都不是
参考答案：D
右心室的肌肉壁最厚．______．
The Web Browser is a simple program that enables a computer to ______ and view pages on the Web.
A．downfall B．downgrade C．downward D．download
