Help 國中基測題組練習

Gary is teaching his students to play a game called “Word House” in the English class. Here is the way to play the game:

Get some pieces of paper that are cut into squares. Each square is for writing one letter only.
Write a letter on one square. For example, write “i.”
Next, take another two squares. Make a two-letter word which contains the letter you have written, for example, “in” or “hi.” Put the new word (written on the two squares) below the first square.
Then make a three-letter word which contains the two letters you have written. Again, put the new word on the next line.
Keep making new words in the same way to build a “word house.” The person who builds the highest word house in twenty minutes wins the game.