How many days did Raju take to complete his assignment? I. Mohit correctly remembers that Raju took more than 3 days and less than 9 days. II. Mina correctly remembers that Raju took more than 7 days and less than 11 days.

Introduction / Context:
The statements give open intervals for an integer day-count. We must see if their overlap isolates a single integer value. We adopt the Recovery-First policy to repair phrasing (“more than x less than y”) to the standard interpretation: x < days < y.

Given Data / Assumptions:

• I: 3 < days < 9 ⇒ possible integer days = {4,5,6,7,8}.
• II: 7 < days < 11 ⇒ possible integer days = {8,9,10}.

Concept / Approach:
Intersect the two integer sets; if the intersection is a singleton, the exact value is determined only when both statements are used together.

Step-by-Step Solution:

Verification / Alternative check:
Check end-point inclusivity: The wording “more than”/“less than” excludes endpoints; 8 remains the sole common integer.

Why Other Options Are Wrong:

• A/B/C: Neither statement alone yields a single value; “either alone” is false.
• D: Together they do yield a unique value.

Common Pitfalls:
Treating “at least/at most” instead of strict inequalities; including endpoints improperly; missing that the domain is integers (days).

Final Answer:
Both statements together are sufficient, but NEITHER alone is sufficient.