This section covers choosing the discard or discards from a tenpai hand that give you the largest wait to win. This entails checking possible waits given a number of slightly different hand makeups.
You should be familiar with an earlier Exam guide, Tenpai Acceptance, before you continue, as this guide uses the framework from that page to systematically determine the correct answer for these types of problems.
Method
In this, you perform the 0/1/2 tile addition from Tenpai Acceptance on each suit, and make a note on the result. Once done, you determine which combinations of tile addition get you to a complete hand (4 groups + 1 pair, 7 pairs, etc), and then for each suit with a “leftover” in it in those combinations, check each tile and see which waits are lost. Add up all the waits you lose if you lose that tile, and the lowest number is your answer.
Example: 
First, set up the Tenpai Acceptance array.
| 0 tiles: 2s 1 tile: 2s+X 2 tiles: 2s+p | p+X 1s+X / p+X 1s+p | p+X 1s+X/p+XX 1s+p | p 1s 1s+X |
Also, note that there are 5 different pairs, so any single tiles is a tenpai wait for 7 pairs.
combinations that work are: 0/1/1/0, 0/1/0/1, 0/0/1/1. Xs are only in the pin and sou, so that is where the answer will be: other suits losing tiles will be unable to make tenpai.
Now, for the possible tiles: put all the tiles that create the patterns that are 1 or greater in the combinations, and 7 pairs: all the 7 pairs waits, and anything that makes a set in pin, sou, or honors.
Now, since we know the answer is in the pin or sou, we go through those one at a time:
8pin: you lose the 7 and 8pin waits.
9pin: you lose the 7 pairs waits, and the 9pin.
3sou: you lose the 7 pairs waits, and the 3sou.
4sou: you lose the 2 and 5sou.
the wait that loses you the least tiles – the fastest – is 8p.
A Warning about Time
Note that this method takes a bit of time. I strongly suggest you leave these sections for last – usually, there are other sections after this on the test with questions of equal value that you can solve much more quickly. Do those first and come back.