The main idea defended by the author in the text is that 
The expression of the text “another tip” (line 5) suggests that the author 
In the fragments of the text: “they may lose the desire to master whatever task you are asking them to do” (lines 12-13) and “then you have to do more than just present lessons in the app” (lines 18-19), the verb forms in bold express the ideas, respectively, of 
In the sentence of the text: “However, if you want people to continue using the app, and use it frequently and often, then you have to do more than just present lessons in the app” (lines 17-19), the connector However can be replaced, without any change in meaning, by 
In the text, the first reason given for an animal to migrate is its
The word in italics that describes the idea expressed in the text by the word in boldface type is
In the text, the third reason given for an animal to migrate is to
In the text, the way day animals succeed in migrating is by
Concerning night animals in the forest, according to the text, their main migration method is by
The expression indie workers, found in lines 10 and 90, refers to
