What was the “liberal consensus,”and how was this related to the Rockefeller Republicans?

The "liberal consensus" was the tacit agreement between the Democratic and Republican Parties in the United States Congress during the 1960s, through which they would support and approve bills related to social security, with the aim of guaranteeing better and greater rights to American citizens.

These policies were mainly promoted by Democratic politicians, who held the majority of the presidency during that decade through John F. Kennedy and Lyndon Johnson. But many moderate Republicans also supported these measures, being led by, among others, Nelson Rockefeller, then-Governor of New York, who drew support from East Coast Republicans for many of the Democratic Party measures.

your answer would be (b)