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 
Considerando o contexto, o termo nothing to do tem o significado apresentado em:
No texto, a expressão and so on pode ser substituída, sem perda de sentido, por:
No texto, o termo aware tem o significado de
O termo therefore no terceiro parágrafo – The characteristics of shape memory alloys are complex and therefore difficult to predict. – implica
In the fourth paragraph, the term thoroughly in – How can a component be produced that has such small dimensions, is elastic, can be thoroughly sterilized and has no joints? – is correctly replaced by
No quarto parágrafo, a expressão make up em – In this case, the acid steals away electrons that make up the bond between nickel and oxygen in the ring. – é corretamente substituída por
In the text, “In addition” means
