The following sentence has a blank. Choose the most appropriate word or phrase to complete it: I was _____________ paying the toll tax.

Introduction / Context:
Fill in the blank questions test a learner's knowledge of collocations and the precise meanings of related words. In this item, the sentence describes a situation where someone does not have to pay a toll tax. The goal is to choose the verb phrase that correctly matches this meaning and forms a natural expression in English.

Given Data / Assumptions:
The sentence is: I was _____________ paying the toll tax. The options include free from, exonerated from, exempted from, exposed to, and another distractor. We assume that the speaker is explaining that due to some rule or condition, they did not need to pay the tax that others were paying.

Concept / Approach:
The key idea is that of official or legal freedom from a duty or payment. The verb exempt and the adjective exempted are used for situations in which a person or group is not required to do something that is normally compulsory, such as paying tax or attending a course. The standard collocation is exempted from paying a tax or fee. Exonerated, on the other hand, is used mostly in legal contexts to mean cleared from blame or accusation, not freed from a payment. Free from is more general and often refers to absence of something unpleasant, like free from disease. Exposed to means subjected to something, usually harmful, and therefore cannot fit the intended meaning.

Step-by-Step Solution:
Step 1: Understand the meaning as I did not have to pay the toll tax due to some rule.
Step 2: Recall that the verb exempt or the past participle exempted is used when a duty or charge does not apply to someone.
Step 3: Match this with the preposition from, forming exempted from paying.
Step 4: Compare other options and note that they either change the meaning or do not collocate with paying a tax.
Step 5: Select exempted from as the most appropriate completion of the sentence.

Verification / Alternative check:
We can test the collocation in a new sentence: Vehicles belonging to emergency services are exempted from paying toll tax. This is exactly how official notifications are often worded. In contrast, exonerated from paying toll tax sounds unusual, because exonerate usually refers to crimes or accusations. The phrase free from paying toll tax is also uncommon as a formal statement. These contrasts confirm that exempted from is the correct and idiomatic choice.

Why Other Options Are Wrong:
Option A, free from, can be followed by a noun like worry or pollution, but is not the usual phrase for official non payment of charges. Option B, exonerated from, deals with removal of blame or guilt and is not used for routine financial obligations. Option D, exposed to, carries the completely different meaning of being subjected to or open to something harmful. Option E, excused to, is grammatically awkward and uses the wrong preposition. None of these reflect the typical phrasing of exemption from tax payments.

Common Pitfalls:
Students sometimes choose exonerated from because they associate both exemption and exoneration with freedom from something, but they overlook the specific context of taxes and charges. A good strategy is to remember that exempted from is used with duties and fees, while exonerated from is used with allegations or crimes. Regular reading of notices, legal forms, and government instructions familiarises learners with these standard expressions.

Final Answer:
The correct completion is exempted from, so the sentence reads: I was exempted from paying the toll tax.