Relativpronomen: dem, der, denen

The Unit 2 trap: the Relativpronomen takes its gender and number from the noun, and its case from its job inside the Relativsatz — or from the preposition in front of it:

• Dativ: dem (m/n), der (f), denen (Pl.)
• with a preposition: vor der, mit dem, für den

Trap: Dativ plural is denen, not den.