Complex sentence: Social and official attitudes to toplessness and nudity had eased by the 1960s and the Hays Code came under repeated challenge, and in 1968 the Code was replaced by the MPAA film rating system.
Split into simpler sentences: Social and official attitudes to toplessness and nudity had eased by the 1960s and the Hays Code came under repeated challenge. In 1968 the Hays Code was replaced by the MPAA film rating system.