Which of the following statements is true?

State-space search is a very general problem solving technique and many problems can be modeled as search

Poker can be solved using state-space search

The cost of a solution is always as least as high as its length

The number of states in the 15-puzzle is roughly $1.8 \cdot 10^{19}$

You are given the state space shown below, where $A$ is the initial state, and $F$ and $I$ are goal states. The numbers on the edges indicate action costs.

Which states are reachable from $G$?
The format of your answer should be as follows (no white spaces, states sorted alphabetically): B,C,D