(a) Grapes: Propagated through cuttings, where healthy vine segments are planted to develop new plants.
(b) Apple: Propagated through grafting, combining a rootstock and scion for improved yield and disease resistance.
(c) Brinjal: Propagated through seeds, which are sown directly or in nurseries for transplanting.
(d) Sugarcane: Propagated through stem cuttings, where mature cane segments with nodes are planted to grow new plants.
Assertion (A): The sum of the first fifteen terms of the AP $21, 18, 15, 12, \dots$ is zero.
Reason (R): The sum of the first $n$ terms of an AP with first term $a$ and common difference $d$ is given by: $S_n = \frac{n}{2} \left[ a + (n - 1) d \right].$