Difficulty: Medium
Correct Answer: Only (II) and (III) follow
Explanation:
Introduction / Context:We combine one existential and one universal premise and check which conclusions are necessary.
Given Data / Assumptions:
Concept / Approach:Let T = Teachers, S = Students, G = Girls. From 'Some T are S' and 'S ⊆ G', we infer (II) Some girls are teachers (those teacher-students are girls) and (III) Some girls are students (since some students exist). The universal claims (I) and (IV) are not supported.
Step-by-Step Solution:
Step 1: Pick x with x ∈ T ∩ S (from the 'some' statement).Step 2: From S ⊆ G, x ∈ G, so x ∈ G ∩ T — validates (II).Step 3: The existence of x ∈ S implies at least one student exists; since S ⊆ G, (III) holds.Step 4: There is no basis for 'All teachers are girls' (I) nor 'All students are teachers' (IV).Verification / Alternative check:Construct a model with many teachers not students and many girls not students; (II) and (III) remain forced while (I) and (IV) fail.
Why Other Options Are Wrong:Options including (I) or (IV) assert unsupported universals.
Common Pitfalls:Overgeneralizing from existence to universals; keep directions of subset relations straight.
Final Answer:Only (II) and (III) follow.
Discussion & Comments