Some students were not involved in the strike. If the above statement is true, which of the following conclusions is/are logically necessary?
1. Some who were involved in the strike were students.
2. No student was involved in the strike.
3. At least one student was involved in the strike.
4. Some who were not involved in the strike were students.
The problem requires identifying which conclusions logically and necessarily follow from the premise: "Some students were not involved in the strike". We will analyze each conclusion based on this premise.
The core premise is "Some students were not involved in the strike." This means that there is at least one individual who fits both criteria: being a student and not being involved in the strike.
The premise only provides information about students who were *not* involved. It does not give any information about students who *were* involved or non-students who were involved. Therefore, this conclusion is not necessarily true.
This statement claims that *all* students were uninvolved. The premise, however, only states that *some* students were uninvolved. It's possible that other students *were* involved. This conclusion is not necessarily true and could even be false.
Similar to conclusion 2, the premise guarantees only that some students were *not* involved. It is logically possible that *all* students were not involved in the strike. If all students were not involved, the premise "Some students were not involved" would still be true. Thus, this conclusion is not necessarily true.
This statement asserts that there exists at least one person who was not involved in the strike and who is also a student. This is exactly what the premise "Some students were not involved in the strike" means. Therefore, this conclusion is logically necessary.
Based on the logical analysis, only Conclusion 4 is a necessary consequence of the given premise.
Consider a linear arrangement of seven bulbs, each of which can be in the ON or OFF states. The initial configuration of the bulbs is shown in the figure. In every Step, the states of the bulbs are changed based on the following rules:
The state of bulbs at the end of Step 1 and Step 2 are also shown in the figure.
The number of bulbs which are ON at the end of Step 8 is ______

Consider a five-digit number PQRST that has distinct digits P, Q, R, S and T, and satisfies the following conditions:
$P < Q$
$S > P > T$
$R < T$
If integers 1 through 5 are used to construct such a number, the value of P is: