Social isolation refers to the objective (A) state of having limited (B) or no social contacts, while loneliness is the subjective (C) feeling of being isolated (D) or lacking social connections.

Explanation

The highlighted words are at their correct position. Hence, “no interchange required” is the correct answer. The given sentence distinguishes between social isolation, which is the measurable condition of having few or no social contacts, and loneliness, which is the personal and subjective experience of feeling isolated or lacking social connections.