Hi, first of all you should be thorough with all of your subjects .Start with the ones in which you have keen interest.It will help you in developing your interest and will help you in deciding your department for  speciality as well. Now coming to your question regarding standard MCQ books I'll suggest you Dental pulse as it includes mcqs topic wise which will help you to know how clear you're with that particular topic,then AIPG book by  Neeraj wadhwan .In this book  the explanation for every question is in elaborated form ,then dentest is also a good book for mcqs .Along with all this you should know your subjects  the most .

All the best for your exams