The new director undertook the responsibility of turning the company around.

undertook 是动词 undertake 的过去式。undertake 由前缀 under-（表示"在...之下"）和动词 take（承担、接受）组成，意思是"承担、着手做（某项任务或责任）"。在句中表示"承担起了"某项责任。