In this sentence improvement question from English usage, you must choose the best replacement for the underlined phrase in the sentence "In case of a natural calamity the shortage of essential things must be overcome in a short time" so that the sentence becomes more accurate and idiomatic.

Introduction / Context:
This question tests your ability to improve a sentence by choosing the most appropriate word or phrase from the given options. In competitive exams this is called sentence improvement or sentence correction. The sentence given is "In case of a natural calamity the shortage of essential things must be overcome in a short time". You must decide which alternative makes the sentence more appropriate in standard English usage.

Given Data / Assumptions:

• The situation described is a natural calamity, such as a flood, earthquake, or cyclone.
• The original phrase is "essential things".
• Options provided include "commodities", "consignments", "material", and "No improvement".
• The aim is to choose the word that best fits the context of public supply and crisis management.

Concept / Approach:
Sentence improvement questions check whether you are aware of standard collocations, or natural word combinations, used in formal English. When talking about food, medicine, and daily necessities during disasters, newspapers and official reports typically use expressions like "essential commodities", not "essential things". Therefore the idea is to replace the vague word "things" with a more appropriate and precise noun.

Step-by-Step Solution:
Step 1: Read the whole sentence and understand its meaning: during a natural calamity there is a shortage of basic necessities.Step 2: Identify the underlined phrase "essential things" and note that it sounds informal and vague.Step 3: Consider the alternatives and ask which word is used in formal English for goods of daily use like food, medicine, fuel, and other necessities.Step 4: Recognise that "commodities" is often used in official language with the adjective "essential" as in "essential commodities".Step 5: Replace "essential things" with "essential commodities" and check whether the sentence now reads more naturally and formally.

Verification / Alternative check:
After substitution, the sentence becomes "In case of a natural calamity the shortage of essential commodities must be overcome in a short time". This sounds like a typical line from a government report or news article and clearly refers to goods required for survival. If you substitute the other options, the meaning becomes less clear or less idiomatic. This confirms that "commodities" is the correct choice.

Why Other Options Are Wrong:
"Consignments" refers to shipments or batches of goods sent from one place to another, not specifically to basic necessities. It does not collocate naturally with "essential" in this context. "Material" is too general and often refers to raw substances or fabric, not directly to food items and medicines for public distribution. "No improvement" would keep the vague phrase "essential things", which is not the best or most formal expression in a competitive exam standard sentence.

Common Pitfalls:
Students sometimes select "No improvement" when they see a generally understandable sentence, but competitive exams demand the most appropriate formal wording. Another pitfall is to confuse "commodities" with "consignments" because both are connected with goods. Remember that "essential commodities" is the standard phrase used in government notifications, legal acts, and news language when referring to basic goods needed in emergencies.

Final Answer:
The correct answer is commodities, because the standard expression in formal English is "essential commodities", which precisely refers to basic goods needed by people during and after a natural calamity.