Step 1: Understanding the Question
We have to place four events in time order, from the earliest to the latest. So we first find the year of each event.
Step 2: Find the date of A: Persian Gulf war.
This war took place in 1990 to 1991, after Iraq invaded Kuwait. It is known as Gulf War I.
Step 3: Find the date of B: Vietnam War.
The Vietnam War lasted from about 1955 to 1975. It is the earliest of the four.
Step 4: Find the date of C: 26/11 attack.
The Mumbai terror attacks took place on 26 November 2008.
Step 5: Find the date of D: 9/11 attack.
The attacks on the World Trade Center in New York took place on 11 September 2001.
Step 6: Put them in order.
From the earliest to the latest we get Vietnam War (1975), Persian Gulf war (1991), 9/11 (2001) and 26/11 (2008). So the order is B, A, D, C.
Step 7: Compare with the options.
Option 1 puts A before B, which is wrong. Option 3 puts C before D, which is wrong. Option 4 starts with A and also puts B late, which is wrong. Option 2 gives B, A, D, C, which matches.
Final Answer:
The correct order is B, A, D, C. This is option 2.