Step 1: Check Assumption I.
The purpose of a probation period is to evaluate} performance before final confirmation. This implies that the employer does not} have complete knowledge of the candidate’s performance at the time of appointment. Hence Assumption I is valid.
Step 2: Check Assumption II.
The very idea of “performance review” during probation assumes the employee will try to prove their worth} during this time to secure confirmation. Therefore, Assumption II is also valid.
Step 3: Conclusion.
Since both assumptions logically follow from the statement, the correct answer is “Both I and II are implicit.”
\[
\boxed{\text{(D) Both I and II are implicit}}
\]