对于估价对象具有潜在的开发价值时，假设开发法几乎是惟一实用的估价方法。 ( )
参考答案：对
25. ---- Ricky, why hasn’t Billy been with us these days?
---- Oh, he is _________for next month’s 400m race.
A．standing out
B．taking up
C．backing out
D．working out
