X元素的阳离子与Y的阴离子具有相同的核外电子排布，则下列比较中正确的是

A．原子序数： X< Y

B．原子半径：X< Y

C．离子半径：X> Y

D．最外层电子数：X< Y

Science and technology is changing fast nowadays. I bought this MP3 player at the beginning of this year but now it's out of ________.

A．date

B．order

C．use

D．sight