The correct answer is option 3: 3, 4, 2, 1.

To find the sequence in which a person travelling from West to East along the 30°N latitude will touch the cities, we need to look at their respective longitudes.

1. Abadan: Abadan is located at approximately 48°E longitude.

2. Basra: Basra is located at approximately 47°E longitude.

3. Cairo: Cairo is located at approximately 31°E longitude.

4. Suez: Suez is located at approximately 32°E longitude.

Since we are travelling from West to East, we will encounter the cities starting with the one that is further west (with smaller longitude) to the one that is further east (with larger longitude) along the 30°N latitude.

So, starting from the westernmost city in the list (3), our sequence would be 3, 4, 2, 1.

Therefore, the correct sequence in which a person travelling from West to East will touch the cities along the 30°N latitude is 3, 4, 2, 1.