( During the Fourth of July weekend in 1947, ) about six milion people crowed onto the beach and into the amusements at Coney Island, "America's Playground" in Brooklyn. NewYork.
A. During the Fourth of July weekend in 1947,
B. It was the Fourth of July weekend in 1947
A, 整句话缺少的是时间状语。如果选B，要么把它做成一个时间状语，或并列句或两个单独的句子
On the Fourth of July weekend in 1947, about six milion people ...
It was the Fourth of July weekend in 1947. About six milion people c...
It was the Fourth of July weekend in 1947, and about six milion people ...
要么做成强调句。
It was on the Fourth of July weekend in 1947 that about six milion people ...