在严寒的冬季，滑雪场的人工造雪机在工作时不断将水吸入，并持续从造雪机的前方喷出“白雾”，而在“白雾”下方，已经积了厚厚的一层“白雪”。对于造雪机在造雪过程中，水这种物质发生的最主要的物态变化，下列说法中正确的是（　　）

A．凝固

B．凝华

C．升华

D．液化

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.