In an offline step, we organize the content of each instance in a graph where each node represents a sentence from the passages and the question. Then, we add edges between nodes using the following topology:

we fully connect nodes that represent sentences from the same passage (dotted-black);

we fully connect nodes that represent the first sentence of each passage (dotted-red);

we add an edge between the question and every node for each passage (dotted-blue). 
 Question: How are some nodes initially connected based on text structure?
we fully connect nodes that represent sentences from the same passage we fully connect nodes that represent the first sentence of each passage we add an edge between the question and every node for each passage