hi,

no there is no restriction to choose pcb or pcm, In questions of SB and SX , there will be four sections in Part I (Physics, Chemistry, Biology and Mathematics) and four sections in Part II (Physics, Chemistry, Biology and Mathematics).  Candidates  may answer any THREE of the four subjects in Part I and any TWO of the four subjects in Part II. In case candidate attempts  more sections, best of three in Part I and best of two in Part II is considered.