Step 1: Start with the Reason and check if it is a real anatomical fact.
Granulocytes (neutrophils, eosinophils, basophils) are white blood cells whose nucleus is not a single round mass. Instead it is pinched into two or more connected lobes, and the lobe count and shape differ from cell to cell. That is exactly what Reason (R) states, so R is a true fact.
Step 2: Now unpack what "polymorph-nuclear" literally means.
Break the word into parts: "poly" means many, "morph" means form or shape, and "nuclear" refers to the nucleus. So "polymorph-nuclear" literally describes a nucleus with many shapes or lobes.
Step 3: Test whether R accounts for that name.
Since granulocytes are named polymorph-nuclear precisely because their nucleus is lobed and variably shaped, the fact in R is the direct cause of the naming in A. Remove the lobed nucleus and the name "polymorph-nuclear" would no longer apply.
Step 4: Confirm Assertion (A) independently.
Textbooks classify granulocytes under the term polymorph-nuclear leucocytes, so A is a correct statement on its own, separate from whether R explains it.
Step 5: Combine the two checks.
A is true, R is true, and R is the actual biological reason behind A rather than an unrelated true fact placed beside it.
Final Answer:
Both A and R are correct, and R correctly explains A, option (1).