Preparation

16 marks would be covered from pgbp or even more than that ,,so even if you prepare whole tax question  may not be asked form the portion u have studied.

so if u are leaving pgbp u might be taking a higer risk

regards

It is suggested to study pgbp at now itself. However you can get exemption even otherwise If your preparation is 100% but as PGBP is important at both level try to remember atleast the concept

I must say...Do not put PGBP for option.. if you are really aiming for an exemption...if you see d past exam papers...minimum 16 to 20 marks qns have been asked from this head only..skipping whole chapter is quit risk...Just go through Prac. manual thoroughly.. Nd RTP it will give you   the conceptual  knowledge/idea abt....try to understand requirement of each provision...

 Read Supplementary Study Paper, RTP, Recent Case Laws, Nd Don’t forget go through Practice manual…some past exam Qns were based on Practice Manual…

Best Wishes...

I would like to suggest you that you shouldn't make option in syllabus bcz there are no any blueprint from ICAI side for Exam Paper. 
If they want, they will ask 50 Marks from PGBP and related chapter. PGBP is main topic in taxation.