Students can enter a response of up to 20 words, which is then graded by matching it against various model answers expressed using a sophisticated patten matching algorithm. See http://docs.moodle.org/dev/The_OU_PMatch_algorithm
This question type was created by Jamie Pratt, working for the Open University (http://www.open.ac.uk/) and has since had many enhancements by OU staff.
This plugin should be compatible with Moodle 3.5+. It is best if you also install the associated superscript/subscript editor plugin. This makes the superscript and subscript options in the question editing form. If the editor is not installed the question type can still be used but these options will not be available.
Install from the Moodle plugins database
Or you can install using git. Type this commands in the root of your Moodle install
git clone https://github.com/moodleou/moodle-qtype_pmatch.git question/type/pmatch
echo /question/type/pmatch/ >> .git/info/exclude
git clone https://github.com/moodleou/moodle-editor_ousupsub.git lib/editor/ousupsub
echo /lib/editor/ousupsub/ >> .git/info/exclude
Then run the moodle update process Site administration > Notifications