Richard was called in by the police to answer questions _______ the disappearance of Thomas Ripley, whose relatives were so ______ his present situation.

A．concerning; concerned about

B．concerned; worrying about

C．with regards to; concerned

D．regarding; concerning about

近年来，企业之间的竞争非常激烈，企业所处的行业与环境都趋向复杂、动态与不确定性的发展中。为了保证企业可持续发展，基于环境的变迁和自身资源与能力的变化，有必要对原有战略进行重大调整，实施战略变革。
(1) 企业变化的层次有哪些
(2) 战略变革的时机如何选择