The correct answer is: C. Either I or II is implicit.
The statement “Though the candidates have been instructed to bring pencils, yet provide some pencils with each invigilator” does not explicitly state whether or not pencils are in short supply or whether or not all candidates will bring pencils. However, the statement does suggest that there is a possibility that either or both of these things could be true.
If pencils are in short supply, then it would be prudent to provide some pencils with each invigilator in case some candidates do not have their own pencils. Similarly, if there is a possibility that not all candidates will bring pencils, then it would also be prudent to provide some pencils with each invigilator.
Therefore, either assumption I or assumption II could be implicit in the statement.