Concept:
- The four options split into two groups: those that accept the Reason as true and those that do not. Deciding the Reason alone therefore halves the work.
- The Reason here repeats a common misconception, which is exactly what the question is testing.
Step 1: Attack the Reason first.
Options (A), (B) and (D) all treat the Reason as true. Only option (C) treats it as false. So if the Reason can be shown false, the answer is settled in one move.
Step 2: Weigh the claim about weapons.
The Spanish forces that entered America were tiny, a few hundred men against states of millions. Numbers that small cannot be explained by better guns and swords alone. Something else must account for the collapse.
Step 3: Name the real cause.
The population of America had been isolated for a very long time and had built up no immunity to diseases from the other continents. Smallpox carried by the Spanish travelled faster than the soldiers themselves and killed on a scale no weapon could match.
So the strongest weapon was biological, not conventional. The Reason is false.
Step 4: Confirm the Assertion stands.
Even with the Reason false, the Assertion itself is correct, since conquest and colonisation were clearly under way by the mid-sixteenth century. A true Assertion with a false Reason is option (C).
Final Answer: (C) Assertion (A) is true, but Reason (R) is false.