Assertion (A): A mango seed will germinate to form a mango tree.

Reason (R): Heredity determines the process by which traits and characteristics are reliably inherited from parents to offspring.

Assertion (A): A mango seed germinates to form a mango tree — this is factually true. A seed always develops into the same kind of organism as its parent plant, because the basic body design (species identity) is faithfully passed from one generation to the next.

Reason (R): As stated in the NCERT chapter (Section 8.2 Heredity): "The rules of heredity determine the process by which traits and characteristics are reliably inherited." This statement is also true — heredity is precisely the mechanism that ensures traits and characteristics of the parent are passed on reliably (accurately, without random change) to the offspring.

Why R correctly explains A: The reason a mango seed grows only into a mango tree (and not, say, a guava tree or some intermediate form) is that heredity ensures the DNA carrying the basic body design and species-specific traits of the mango plant is transmitted faithfully to the seed and hence to the seedling. Since the mechanism described in R (reliable inheritance of traits/characteristics from parent to offspring) is exactly why the seed's outcome (A) is what it is, R is the correct explanation of A.

Why the other options are wrong:

• (B) would be correct only if both statements were true but unrelated in a cause-effect sense; here R directly explains why A happens, so (B) is incorrect.
• (C) is wrong because R is not false — it is a direct paraphrase of the chapter's definition of heredity.
• (D) is wrong because A is not false — a mango seed germinating into a mango tree is a true, everyday biological observation, not a false statement.