____ the young people keep learning it, they can pass on Dai culture from generation to generation.

A．Even though

B．As soon as

C．As long as

D．As though

某班第一个班投入原料A、生产成品B、成材率C=B/A×100%。第二班投入原料D生产成品E成材率F=E/D×100%。列出计算这两个班累积成材率的表达式。