Music artist: who did "stranger in a strange land" in 1971?

Questions

Who ate watercress to dissolve gravel and stones in the bladder?

Who authored 'ivanhoe'?

Who became a genius whenever he put on the fabulous kurwood derby?

Who became president of south africa in 1989?

Who became the first father-and-son team to win oscars for the film 'treasure of sierra madre'?