Choose the sentence that correctly and idiomatically uses the expression make light of difficulties.

Introduction / Context:
This sentence improvement item revolves around the idiom make light of something, which means to treat a serious problem as if it were not important. The question examines both your knowledge of the fixed preposition in the idiom and your awareness of correct verb forms and word order in a complex sentence.

Given Data / Assumptions:
The basic message is that Monu and Sonu tried to minimise their problems, but in reality the situation was bad. Options differ in how they combine make light, the preposition of, and the object their difficulties. One option also changes the verb form has attempted, which affects agreement with the compound subject Monu and Sonu.

Concept / Approach:
In standard English the idiom is make light of something, not make light something or make something light in this sense. When we say make light of their difficulties, we mean that they treat the difficulties as unimportant. Additionally, with the compound subject Monu and Sonu, the correct auxiliary in the past perfect or present perfect would be have, not has. In this sentence the simple past attempted is already correct and does not need to change.

Step-by-Step Solution:
First, examine option A: make light of their difficulties. This matches the idiom exactly and keeps the rest of the sentence intact.Second, examine option B: make their difficulties light. This changes the idiomatic structure into a literal and slightly odd phrase. It sounds as if they are physically making difficulties light in weight.Third, look at option C. It uses has attempted with Monu and Sonu, which creates a subject verb agreement error, and it still omits the preposition of.Fourth, look at option D. It keeps attempted, but uses make light their difficulties without of, which is not the standard idiom.Finally, compare all options. Only option A uses the correct idiom in a grammatical and natural sentence.

Verification / Alternative check:
You can verify the idiom by recalling similar phrases, such as make light of a serious issue, make light of an accident, or do not make light of this warning. In all of these, the preposition of is always present. Expressions without of may appear in some very old or poetic texts, but they are not used in modern exam level English, so you should follow the standard pattern.

Why Other Options Are Wrong:
Option B treats difficulties as an object complement of the adjective light and loses the idiomatic sense. Option C introduces a grammatical error by pairing has with a plural subject and still fails to include the necessary preposition. Option D is grammatically closer but still incomplete because native speakers say make light of something, not make light something in this context. For these reasons, options B, C, and D must be rejected.

Common Pitfalls:
Many students know the basic words in an idiom but forget or change the small connecting words, especially prepositions. However, in idioms these small words carry crucial meaning, and exam setters often target them. Another common issue is to change tense or agreement without any need, which creates new errors rather than fixing the original one. When improving a sentence, always ensure that the rest of the structure remains correct.

Final Answer:
The correct sentence is Monu and Sonu attempted to make light of their difficulties, but it was obvious that things were going badly for them.