Question

why do we say that China rose is a complete flower?

Answer 1

In order for a flower to be considered complete it must have four parts: sepals, petals, stamens and pistils. Incomplete flowers lack one or more of these parts. As China Rose has every part necessary for a complete flower, its called a complete flower...

Answer 2

china rose has all the necessary parts of a complete flower so we say that 
it is a complete flower .