Which of these can be found in both gymnosperms and angiosperms

The answer is C. Ovule. 
A gymnosperm is a woody tree like a fir tree. It does not bear flowers or fruit. Its seeds are naked, as they are not covered by a fruit wall and are arranged in a cone-like structure. 
An angiosperm is a group of plants that consists of herbs, shrubs and trees. The angiosperms bear flowers and fruit. Its' seeds are not naked as they are covered by the fruit wall.