In the sentence, certain words are in bold and numbered from A to E, which are the possible pairs to be interchanged. Choose the pair(s) of words which need to be interchanged to make the sentence grammatically correct and meaningful. 

The ache of loneliness (A) pangs us to (B) seek out social connection just as hunger (C) drives urge us to eat and the idea is (D) intuitively satisfying, yet it has long (E) proved difficult to test in humans.