救生圈的颜色应以（）。

“客里空”

（）的决策属于单目标决策。

A.企业对外投资

B.企业新产品开发

C.企业当年总产值或利润额

D.企业设备更新改造

Leonardo da Vinci ________ birds kept in cages in order to have the pleasure of setting them free.

A．is said to be buying

B．is said to have bought

C．had said to buy

D．has said to have bought

乳痈的发病机理是（）

A.厥阴气滞，阳明蕴热

B.气血瘀滞，经络阻隔

C.肝气郁结，脾失健运

D.冲任失调，肝肾亏损

E.脏腑失调，经络阻隔

遵守礼遇适度的原则，需要重视哪些问题？