How to create a file of problems
1 Open the notepad.
2 Write the words to highlight.
3 Write the sentence of problem.
4 Write the sentence of answer.
5 Write an empty row.
6 Repeat the 2-5.
7 save the file in UTF-8.(For download version, not UTF-8 but 1-2byte character set.)
About the word to highlight.
If there is @ in front of the word , the word will not be visible.
About the sentence of problem and the sentence of answer.
It need . at the end of sentence.