What should be put into the space "a"? Figure 2 is the array representation of a binary tree shown in Figure 1.

The correct answer to this question is 4. Binary trees are used in computer science. As the name suggests, it is a tree structure which contains data information. Its tree has root and nodes, which are commonly referred to as children. There are left children and right children. In the binary tree provided, 200 is the root. 220 is the right child, and 180 is the left child.

Then, 180 becomes the root, and 190 is the right child and 150 being the left one. From there, 150 is the root, and it only has one left child, which is 130. Binary trees can also include empty sets, but this particular tree doesn't.