Statement — Please send an official letter rather than a semi-official letter on this subject this time.\n\nAssumptions —\nI. The format and emphasis of different types of letters are different (official vs. semi-official).\nII. It is possible to send different types of letters on the same subject depending on context.

Introduction / Context:
The instruction specifies the type of communication to be used “this time,” implying that letter types differ materially and that the same subject can be handled through alternative formats depending on the situation. This presupposes a recognized difference in formality, tone, or legal weight between “official” and “semi-official,” and that the sender has discretion to choose the appropriate type for the present need.

Given Data / Assumptions:

• Request: use an official letter now, not a semi-official one.
• I: official and semi-official letters differ in format/emphasis/authority.
• II: multiple letter types can address the same subject in different instances.

Concept / Approach:
Without I, the instruction would be pointless because the two formats would be indistinguishable. Without II, the phrase “this time” would be odd, as it implies variation across occasions. Hence both are required.

Step-by-Step Solution:

Verification / Alternative check:
If formats did not differ or alternatives were not allowed, the instruction would be redundant or impossible, confirming both assumptions are needed.

Why Other Options Are Wrong:

Common Pitfalls:
Missing the significance of “this time” as a cue for II.

Final Answer:
Both Assumption I and II are implicit.