Step 1: Recall the UNSC structure.
The UN Security Council has 5 permanent members and 10 non-permanent members.
Step 2: Note the term.
Non-permanent members are elected for a fixed term of two years by the General Assembly.
Step 3: Understand the rotation.
Every year 5 of them are replaced and 5 continue, which keeps the Council working smoothly.
Step 4: Rule out the others.
One year is too short, and three or four years are not provided in the Charter.
Answer: Two years (Option 2).