the following diagram shows the logic gates...n 2nd pic is what i got as Boolean expression...just want to make sure if it is correct or can simplify it more...
thanks for the help

 

Yes, what you have so far is correct.

Yes, it can be simplified further.

Focus on the two terms that do not involve D. Do they share any factors that can be factored out? What happens to what is left?

 

A" B" and C' can be factor out right...only D cant