The logic followed is:The two main (and most important) parts of a rose plant are the stamen (male component) and the pistil (female component). Other parts include the petals, sepals, leaves, and stems. Each of these also contains sub-parts that are all responsible for the growth and reproduction of the plant.The petals refer to the blooms of a flower.They are comprised of cellulose and other organic material.They are basically, modified leaves that surround the reproductive structure of the flower.Collectively, the petals are known as the corolla. There are specific characteristics pertaining to the rose. These include the following:It contains multiple stamensIt has leaves that grow in alternate patterns on the stemIt is symmetrical in shapeIt has unconnected petals that number in five or multiples of fiveIt contains prickles or thrones on the stems, which vary in size, shape and amount and can be used to identify one species of rose from anotherIt has bisexual reproductive partsThus we can say a rose flower always has petals out of all the given options. If it would have asked about a plant, it always has the roots but the question is talking about flowers. So flowers always have petals.Hence, the correct answer is "Petals".