In 2018, which of the following countries had legalized the possession and use of recreational cannabis (marijuana) for adults?

Introduction / Context:
This general knowledge question tests awareness of international drug policy and recent changes in laws on recreational cannabis. Competitive exams often include current affairs related to social policy and legal reforms because they reflect how different countries approach public health, crime control, and individual freedom. Here, the focus is on identifying which countries had fully legalized the possession and use of recreational cannabis by about 2018, not just medical use or partial decriminalisation.

Given Data / Assumptions:

• Statement 1 refers to America, that is, the United States of America.
• Statement 2 refers to Canada.
• Statement 3 refers to Nigeria.
• Statement 4 refers to Uruguay.
• The question asks about legalization of possession and use of recreational cannabis at the national level, not just in some regions.

Concept / Approach:
The key concept is the difference between full national legalization, regional legalization, and decriminalisation. A country is treated as having legalized recreational cannabis only if the national law permits adults to possess and use cannabis, usually with regulation and taxation. If only some states or provinces allow it, but national law does not, that is not a full country level legalization.

Step-by-Step Solution:
Step 1: Recall that Uruguay was the first country in the world to fully legalize recreational cannabis through national legislation. Step 2: Recall that Canada passed national legislation to legalize recreational cannabis, and the new law came into effect in 2018. Step 3: The United States has some states that permit recreational cannabis, but it is not legalized at the federal level, so the whole country cannot be counted. Step 4: Nigeria does not have laws that legalize recreational cannabis; possession remains illegal. Step 5: Therefore, only statement 2 (Canada) and statement 4 (Uruguay) are correct.

Verification / Alternative check:
Another way to check is to remember a basic timeline. Uruguay is known as the first country to legalize recreational cannabis at the national level. Canada is widely known as the first major industrialised nation to do so, with a law implemented in 2018. The United States is often mentioned in news because several states allow recreational use, which can confuse learners, but the federal classification of cannabis remains restrictive, so it is not a full country wide legalization. Nigeria is never listed among legal cannabis countries. This confirms that only countries 2 and 4 match the condition in the question.

Why Other Options Are Wrong:
Option 1 (1, 2 and 3) is wrong because America and Nigeria have not both fully legalized recreational cannabis nationwide.
Option 3 (1 and 4 only) is wrong because the United States is not fully legalized at the national level.
Option 4 (1, 2 and 4) is wrong for the same reason; it wrongly includes America with Canada and Uruguay.
Option 5 (1, 3 and 4 only) is also wrong because it includes Nigeria, which does not have legal recreational cannabis.

Common Pitfalls:
A common mistake is to assume that because some states in the United States allow recreational cannabis, the whole country counts as legalized. Exam questions often exploit this confusion. Another pitfall is ignoring the difference between medical cannabis laws and recreational cannabis laws. Students must carefully distinguish between partial decriminalisation, medical use permission, and full adult use legalization at the national level.

Final Answer:
The correct combination of countries that had legalized recreational cannabis at the national level by 2018 is 2 and 4 only.