strict binary tree is a tree which has either "0" children OR "1"children . AND
A n-ary tree is a tree which has either "0" children OR "n" children , Which means that n-ary tree is also a strict binary tree , so
we know property of n-ary tree that if 'i' is no. of internal nodes of complete n-ary tree ,
the no. of leaves in it = i( n-1) +1
so According to question no. of leaves = 19 [given] ,
and as BInary tree so n=2
19= i(2-1) +1
19= i+1
i=18 ; internal nodes= 18 , no. of leaves = 19
so 18 + 19 = 37 (total no. of nodes ) option B is anwser