人民解放军挺近大别山的重大军事行动，标志着

A．解放战争开始转入战略进攻

B．解放战争战略决战的开始

C．淮海战役结束

D．南京国民政府被推翻

Natural selection is defined as the process ______ the course of evolution by preserving those traits best adapted for an organism’s survival.
A. to which directs B. of which directs it
C. directs it D. that directs