**Assertion (A):** Meiosis I is called "reductional division." **Reason (R):** Sister chromatids separate during anaphase I, halving the chromosome number.

**Assertion (A):** Neurons are permanently in G0 phase. **Reason (R):** G0 phase is a stage where cells are resting but can always be stimulated to re-enter the cell cycle.

**Assertion (A):** Crossing over increases genetic diversity in offspring. **Reason (R):** Crossing over produces new combinations of alleles by exchanging segments between non-sister chromatids of homologous chromosomes.

**Assertion (A):** Cleavage furrow formation is absent in plant cell cytokinesis. **Reason (R):** Plant cells have a rigid cell wall that prevents the inward constriction required for cleavage furrow formation.

**Assertion (A):** After S phase of the cell cycle, DNA content doubles but chromosome number remains unchanged. **Reason (R):** Sister chromatids produced during S phase are joined at the centromere and counted as a single chromosome.