We can quickly find by eliminate the incorrect ones.
Option A) is incorrect as it is lexicographically smaller than ((1,0),c,(1,1)) so can't come next
Now, all remaining are lexicographically greater than ((1,0),c,(1,1)) and so are possible candidates for next element. Here the thing to realize is that the next element must be smallest of all possible next candidates because if it wasn't then it cannot create the lexicographic order.
So we find the smallest of candidates from option b,c,d is option C) ((1,1),a,(0,0))
