Fill in the blank with the appropriate Modal.

I ________ pass my examination because my parents have toiled a lot for my education.

have to

The correct answer is Option (3) - have to

The appropriate modal to use in the sentence is "have to". This modal indicates necessity or obligation, which fits the context since the sentence explains that the speaker must pass the examination due to their parents' hard work.

So, the complete sentence is:

I have to pass my examination because my parents have toiled a lot for my education. ****