1) Optimal binary tree can be efficiently constructed using dynamic programming.
2) Breadth-first search and Depth-first search both can be used to find the connected components in a graph.
3) To construct a tree uniquely one of the following combinations should be present:
i) infix and prefix or,
ii) infix and postfix.
with prefix and postfix tree can be constructed but not uniquely.
so, option b is false.