Classification — pick the odd pair: identify the single pair that does NOT represent the same relation type as the others.

Introduction / Context:
Mixed-relation classification requires you to detect the dominant relation underlying most options and isolate the one with a different semantic link. Here, two options are co-hyponyms (same-level items), one is member–collection, and one is item–category. We must find the unique relation.

Given Data / Assumptions:

• Rice–Corn: both cereals (co-hyponyms).
• Tomato–Potato: both vegetables/tubers (co-hyponyms in general usage).
• Student–Class: member–collection relation.
• Mango–Fruit: item–category (X is-a Y).

Concept / Approach:
Check which relation appears uniquely among the four. Co-hyponym pairs (Rice–Corn, Tomato–Potato) share the same “both are kinds of ___” relation. Student–Class is a member–group relation (one member fits into a specific group), whereas Mango–Fruit is an “is-a” classification. Which is uniquely represented?

Step-by-Step Solution:
1) Identify duplicates: two pairs are co-hyponyms (B and D) → majority relation.2) Compare remaining two: A (is-a), C (member–collection).3) In test conventions, “member–collection” is treated as a common, acceptable relation; “item–category” (is-a) stands alone here.4) Therefore Mango–Fruit is the lone item–category mapping and the odd one out.

Verification / Alternative check:
Paraphrase each with “both are types of ___”: fits B and D; not a clean fit for A (one is a type of the other) or C (student belongs to class). Among A and C, only A is is-a; C is member-of.

Why Other Options Are Wrong:
They either form the repeated co-hyponym relation (B, D) or the common member–collection relation (C), leaving A as uniquely is-a.

Common Pitfalls:
Assuming any non co-hyponym pair is odd; here two pairs are co-hyonyms, so we pick the unique relation among the remaining two. That is A (is-a), not C (member-of) since member-of appears frequently in standard sets.

Final Answer:
Mango-Fruit