Robert A.Heinlein was considered one of American's "Big Three"western science fiction   authors,along with Issac Asimov and Arthur C.Clarke.He was born in a family of seven   children in 1907,attended public school in Kansas City,and graduated from Central High   School in 1924.In 1929 he graduated from fhe U.S.Naval Academy at Annapolis,and served   as all officer in the Navy.This experience had a strong influence on his character and writing.At the age of thirty-two,he turned his hand to writing science fiction.     Heinlein's first published stories appeared in the action-adventure magazine Astounding   Science Fiction in 1939.Under his influence writers started to examine how technology might   affect the everyday lives of ordinary people,and society in general.     Heinleiu's early works emphasized adventure,and were aimed at young readers.In 1959   he received the Boy's Clubs of American Book Award.In these novels Heintein avoided open   didacticism ,although his main characters learned lessons in courage and tolerance.Beginning in the late 1950s,Heinlein started to write specially for adults,and to deal with such topics as cloning,religion,and free love.     Heinlein produced fifty novels and collections of short stories during his career.One of his best-known works is the novel Stranger in a Strange Land,published inl961.A few years later it was adopted by the"Peace and Love"generation,and became the most successful       science-fiction novel ever published.Glory Road(1963),written in the tradition of Edgar Rice   Burroughs's Mars stories,is another of his most popular works.       Within the framework of his science fiction stories,Heinlein repeatedly addressed such   social themes as the importance of self-confidence and the duties each person owes to the   society.In his fiction,Heinlein coined words that have become part of the English language,  including"grok"and"waldo".He also described a modern version of a "waterbed"in his novel The Door Into Summer and several of his works have been adapted for film and television. Which of the following is true about Heinlein's works?
They were Never aimed at adults. They forced readers to accept moral ideas. They were greatly influenced by other writers. Early works were popular among young readers.