The International Day for Monuments and Sites, also known as World Heritage Day, is observed globally to promote awareness about cultural heritage and historical monuments. On which date is this day celebrated each year?

Introduction / Context:
The International Day for Monuments and Sites, widely known as World Heritage Day, highlights the importance of preserving architectural and cultural landmarks for future generations. It encourages communities and governments to value conservation, restoration, and sustainable tourism. Knowing the date of this observance is important for examinations that cover UNESCO activities, world heritage issues, and important international days.

Given Data / Assumptions:

• The event has two common names: International Day for Monuments and Sites and World Heritage Day.
• It is observed annually on a fixed date.
• The question offers four dates in April as possible answers.
• We must select the exact date that matches UNESCO and international practice.

Concept / Approach:
The correct date for the International Day for Monuments and Sites is 18 April. The International Council on Monuments and Sites and UNESCO support events and campaigns on this day each year. The approach is to remember that this day falls in the middle of April, specifically on the eighteenth, and to distinguish it from other observances that are clustered around late April such as National Civil Services Day in India.

Step-by-Step Solution:
Step 1: Recall that World Heritage Day is celebrated in April, not in any other month.Step 2: Recognise that the correct date is 18 April as per UNESCO and heritage related calendars.Step 3: Check the options and find that 18 April is listed as option B.Step 4: Note that other options such as 16 April, 19 April, and 21 April are close but do not match the official date.Step 5: Mark option B as the correct choice.

Verification / Alternative check:
You can verify this by recalling that many world heritage events and seminars often mention the date 18 April in their titles and reports. United Nations and UNESCO websites also list 18 April as the International Day for Monuments and Sites. Some exam oriented material explicitly suggests remembering 18 April as World Heritage Day, which further confirms your answer.

Why Other Options Are Wrong:
19 April is one day after the correct date and is sometimes included to confuse those who only vaguely remember that the day falls in the third week of April.

21 April is used for other observances, for example National Civil Services Day in India, and is therefore not correct here.

16 April is also a nearby date but does not correspond to the official UNESCO observance for monuments and sites.

Common Pitfalls:
A common mistake is to mix up 18 April with other April dates related to civil services, health, or national events. Because many significant days fall in April, candidates may have a mental block and end up guessing. To avoid this, you can group related days together in your notes, such as placing 18 April for heritage, 21 April for civil services in India, and 22 April for Earth Day. This thematic grouping makes it easier to recall the correct date during exams.

Final Answer:
The correct date is 18 April.