Solution: Chasmogamous flowers are flowers that have open petals such that the pollen and stigma (the reproductive organs) are exposed to allow cross-pollination. On top of that chasmogamous flowers are large, colorful, and scented flowers to attract pollinators.
Cross-pollination cannot occur in cleistogamous flowers, because they are small, closed flowers with unexposed reproductive organs. However, they undergo self-pollination since the reproductive organs (stigma and anther) are present near each other.