How much silica do silica refractories usually contain?

• A. 95 ‚Äö√Ñ√∂‚àö√ë‚àö¬® 97%
• B. 0.2 ‚Äö√Ñ√∂‚àö√ë‚àö¬® 1.0%
• C. 1.8 ‚Äö√Ñ√∂‚àö√ë‚àö¬® 3.5%
• D. 0.3 ‚Äö√Ñ√∂‚àö√ë‚àö¬® 0.9%