For the manufacture of Portland cement, the proportions of raw materials used, are

A. Lime 63% ; silica 22% ; other ingredients 15%

B. Lime 22% ; silica 63% ; other ingredients 15%

C. Silica 40% ; lime 40% ; other ingredients 20%

D. Silica 70% ; lime 20% ; other ingredients 10%

Answer: Option A