Which of the following is true

A．Male insects are always smaller than females.

B．In a given species nature provides differences between sexes to secure successful production.

C．Size and strength protect females from other females.

D．Longevity is characteristic of the Dynastes and Megasoma.

为提高挖掘机得胜产能力，应使装卸工作循环中的各工序紧密配合，做到稳、准、快、满和（）。