Residents ________ not to go out alone or to take part in any groups during the period of recent terrorist activities.

A．were always being warned

B．are always warning

C．always warned

D．had always been warned

下列企业素质中，能成为企业灵魂和精华的是（）

A.人员素质

B.技术装备素质

C.管理素质

D.文化素质