In a flower, there are five unequal petals. The posterior petal is the largest. The two anterior petals are partially fused to form a boat shaped structure. The two lateral petals are smaller than the posterior petal.Which one of the following characters is not associated with such a flower?

• A. The odd sepal is anterior
• B. The aestivation of the petals isdescendingly imbricate
• C. The pollination is by piston mechanism
• D. The number of carpels is many