They have been living in Switzerland ________ seven years.
They have been living in Switzerland ________ seven years.
Explanation
They have been living in Switzerland for seven years.
وہ سات سال سے سوئٹزرلینڈ میں رہ رہے ہیں۔
The word "for" is used to indicate the duration of time during which the action (living in Switzerland) has been happening.
This usage is common when talking about actions or states that have been ongoing for a specific period.