由于生活水平的提高，人类性成熟的时间也不断（）。
参考答案：提前
劳动者享受权利，应以履行劳动者义务为前提。[ ]
China's first Mars probe，Yinghuo1，was launched in the second half of the year 2011 and it was the
first time that China ________ another planet.[ ]
A．explored
B．researched
C．discovered
D．invented
