Answer is a)
say n=4
According to answer d no of comparisons will be 3
but actually there will be 4 comparison
1<=4
2<=4
4<=4
and final comparison will be 8<=4 which will give false ,So total no of comparisons are 4 So d cant be true
Moreover say for 7 node no of comparisons will be
1<=7
2<=7
4<=7
8<=7 i.e also 4
so answer is ceil (logn)+1 i.e option a