c is Incorrect.
BST cannot have same shape for particular set of data
Suppose you have to insert three elements
Input sequence matters in a BST
Suppose you have input sequence
1,2,3
BST will be
1
2
3
But if your input sequence is 3,2,1
Then your tree will be like
3
2
1
For particular set {1,2,3} you can have many BST possible and shape changes.
Now answering your doubt
A BST with a set of elements always have multiple links per node.
This statement is correct because A BST is a Structure where each node has more than 1 links, one pointing to the left sub tree and one pointing to the right sub tree
Struct node *BST{
int data
node *left;
node *right;
}s;
Thanks