Require Column D Based on Column C Answer

I have a dropdown choice in column C (yes/no). I need column D to be a required field if the answer in column C is "yes". That needs to be a dropdown box with "yes/no" choices. 

Example: If the dropdown choice in C2 is "yes", then D2 HAS to be answered "yes or no". If C2 is "no", D2 does not need to be completed. The answers in column D need to be based on the answer in column C.