Answer:
Right after reading it first time.
Step-by-step explanation:
Rereading is a powerful instructional strategy that assists the readers to decode the meaning of the text or passage. Thus, while reading a text, if the reader comes across difficulties to understand a particular passage, he/she requires to reread it immediately after reading it for the first time as it would assist in having a better understanding and clarity of the thought. The second option is incorrect as without understanding the middle paragraph or passage the meaning of the remaining would be incomplete. Rereading whole text would consume unnecessary efforts and time, so the third is also incorrect. The fourth one suggests reading the text again after reading something else that would again distract as the flow would be broken. Thus, all we are left with is the first one as the correct option.