Answer:
a) any technical terms that most readers would be unable to define
Step-by-step explanation:
When writing an explanatory text, you have to make sure that your audience understands everything you are talking about so you have to make sure that the technical terms mentioned in the text is defined for clearer understanding.
Technical terms that are used more than once in the text is not necessarily needed to be defined because the reader would be able to use context clues and have an idea of what it means
The other choices are not needed to be defined either