Correct Answer - D
`**` Pollen grains of many species cause severe allergies and bronchial affictions in some people leading to chronic respiratory disorders-asthma, bronchitis, etc.
`**` In some members of Rosaceae, Leguminoseae and Solanaceae, they maintain viability for months.
`**` In some cereals such as rice and wheat, pollen grains lose viability within 30 minutes of their release.