What is the amount of sea coal needed in cast irons for large green casting moulding sands?

What is the amount of sea coal needed in cast irons for large green casting moulding sands?
A. 10%
B. 15%
C. 20%
D. 25%
Right option is A. 10%

Explanation: Sea coal otherwise is used in small numbers for binding. Sea coal is used for surface appearance improvement. It is used about 10% in cast iron moulding sands for large green casting sands.