National Volunteer Day, observed to promote the spirit of voluntary service, is celebrated on which of the following dates?

Introduction / Context:
This question checks a specific factual detail about National Volunteer Day, a day associated with celebrating and encouraging voluntary service. Exam questions on important days often include such observances to test whether learners can recall less common but socially significant dates, beyond the most famous international days.

Given Data / Assumptions:

• The observance mentioned is National Volunteer Day.
• The focus is on the calendar date, not on the year or the country specific variations.
• The options include four dates in September and October and one extra date linked with another volunteer related observance.

Concept / Approach:
The main approach is factual recall, supported by elimination:

• Remember that National Volunteer Day in commonly referenced general knowledge questions is associated with 21st September.
• Note that other dates in the options belong either to different observances or are simply distractors.
• Select the date that matches standard exam and general knowledge sources.

Because some countries have their own versions of volunteer days, exam questions typically follow a standard reference used in common GK material, which you should memorise accordingly.

Step-by-Step Solution:
Step 1: Identify that the question is asking for National Volunteer Day, not International Volunteer Day or other similar sounding events. Step 2: Recall from general knowledge reading that National Volunteer Day is commonly associated with 21st September in exam oriented material. Step 3: Scan the options to find 21st September. Step 4: Recognise that 1st October, 11th October and 29th September are other dates used for different events or included to confuse candidates. Step 5: Note that 5th December is linked with International Volunteer Day, not National Volunteer Day in this question context. Step 6: Conclude that 21st September is the correct choice here.

Verification / Alternative check:
Verification can be done using standard competitive exam question banks or online GK practice sets where this exact multiple choice question appears and 21st September is treated as the correct answer. It is important to match your answer with the reference pattern used in the question bank or syllabus you are preparing from, because naming and dates can vary across countries and organisations.

Why Other Options Are Wrong:
1st October: Sometimes associated with other observances such as voluntary blood donation day, but not the reference used here. 11th October: Not the commonly accepted date for National Volunteer Day in exam material. 29th September: Also not used for this specific observance in standard GK references. 5th December: This date is widely known for International Volunteer Day, which is related but different from the National Volunteer Day asked in this question.

Common Pitfalls:
Learners often confuse National Volunteer Day with International Volunteer Day and mistakenly choose 5th December. Others guess 1st October or 29th September because they look familiar or fall near other social observances. The best way to avoid such confusion is to build a small table of days related to volunteering: for example, National Volunteer Day on 21st September in this exam context, and International Volunteer Day on 5th December, each with a clear mental association.

Final Answer:
National Volunteer Day, in the context of standard exam general knowledge, is observed on 21st September.