"Why aren't you studying right now?"
Translation:¿Por qué no estás estudiando ahora mismo?
If the purpose of this lesson is to show how to stress how a word changes when it is right now. As is in this sentence ¿Por qué no estás estudiando ahora mismo? "estudiando" should not need a closing statement "ahora mismo" It would be different if the sentence were ¿Por qué no estás estudias ahora mismo? This would be more in line with stressing that fact the it is right now and does not say it twice in the same sentence.