Self-assessment activities are of four types:

• Drag and drop onto image (ddi) exercises allow learners to check if they can find their way around a sketch or a chart. They operate by simple drag and drop;

• Gap-fill exercises (gfe) with a contextual image require a little more concentration on the reader's part, but is very fruitful in ensuring that difficult concepts are well understood. From a pedagogical point of view, it is an excellent exercise because they are asked to rephrase what has been presented in the book in order to construct sentences that make sense, the missing texts being offered in drop-down menus;

• Categorization exercises (cat) complement the previous two activities well: readers organize elements into categories and thus learn to distinguish their characteristics;

• Finally, single-choice questions and multiple-choice questions (quiz) allow them to test their knowledge in a fairly broad way, but they are not very user-friendly tools.