An inference is making an educated guess based on information. Here is a tip to help you out in the future. If you know the definition of the word inference, then plug all of the answers into the blank, but replace the word "inference" with its definition. For example:
1) An educated guess based on information is necessary to understand a text.
2) An educated guess based on information is necessary to read a text.
3)An educated guess based on information is necessary to interpret a text.
4)An educated guess based on information is necessary to analyze a text.
My answers would be:
Understand, Interpret, and if you require a 3rd answer, analyze. You can read a text with your eyes.