Have you any idea _______?

A．that how we can improve the English level within 4 months

B．that how can we improve the English level within 4 months

C．how can we improve the English level within 4 months

D．how we can improve the English level within 4 months

铁路基本建筑限界图上的横向尺寸由线路中心算起，高度由（）算起。