**Assertion (A):** Sieve tube elements can survive without a nucleus. **Reason (R):** Companion cells, which are nucleated and metabolically active, provide proteins, hormones, and metabolic support to sieve tube elements through plasmodesmata.

**Assertion (A):** Monocot stems cannot undergo secondary growth. **Reason (R):** Vascular bundles in monocot stems are closed (lack cambium), so the production of secondary xylem and phloem is not possible.

**Assertion (A):** The ovary of Brassicaceae appears bilocular but is technically unilocular. **Reason (R):** In Brassicaceae, the ovary has parietal placentation with a false septum (replum) that divides it into two apparent chambers, but the replum is not a true septum.

**Assertion (A):** The sunflower "flower" as seen by the naked eye is an inflorescence, not a single flower. **Reason (R):** It is a capitulum (racemose inflorescence) consisting of many ray florets at the periphery and disc florets in the centre, all on a common flattened receptacle.

**Assertion (A):** Potato is classified as a stem modification, not a root modification. **Reason (R):** Potato has "eyes" which are axillary buds at nodes, confirming its stem identity.