What have given mankind a new viewpoint on the earth and its neighbors in space

A．That people dreamed of leaving their home planet and exploring other worlds became reality.
B．After the Apollo program, the emphasis in piloted missions shifted to short-duration spaceflight.
C．Space exploration is a great challenge to human beings and will be achieved through generation's work.
D．Today efforts focus on keeping people healthy during space missions and in increasing the cost of sending satellites into orbit.

A．While the Global System for Mobile Communications (GSM) radio network stretches around the globe, the amount of data which can be transmitted over it is only a small bit.
B．Wireless Local Area Networks (WLANs) has the advantage of broadband, but their local transmitting area is limited.
C．New wireless transmission techniques such as Bluetooth can send data without cables within about ten meters.
D．Until now, any user can move freely between old connection coverage areas and the new network.