The correct answer is: A. Only assumption I is implicit
The statement says that the integrated steel plants in India would no longer have to depend on imports for continuous casting refractories. This means that India currently imports continuous casting refractories, but will be able to produce them domestically in the future.
Assumption I is that continuous casting refractories are needed by India. This is a necessary assumption, because if India does not need continuous casting refractories, then there is no reason why the integrated steel plants would need to produce them domestically.
Assumption II is that continuous casting refractories are in demand. This is not a necessary assumption, because even if continuous casting refractories are not in demand, the integrated steel plants may still choose to produce them domestically in order to reduce their reliance on imports.
Therefore, only assumption I is implicit in the statement.