根据以下内容回答题：Doris Lessing，a novelist whose books have swept across continents and reflect the concern about the social and political issues of her time，won the 2007 Nobel Prize in Literature．The award comes with about$1．6 million． Ms Lessing never finished high school and largely educated herself through reading．She has written dozens of books of fiction，as well as plays，nonfiction and two volumes of autobiog-raphy．She is the l l th woman to win the Nobel Prize in Literature． Ms Lessing was born Doris May Tayler in 1919 in what is now Iran．Her father was a bank clerk，and her mother was trained as a nurse．Attracted by the promise of farming riches，the family moved to Zimbabwe，where Ms Lessing had what she has called a painful childhood． She left home when she was 1 5．and in 1 937 she moved to Salisbury in southern Rhodel-sia，where she took jobs as a telephone operator and nursemaid．She married at 19 and had two children．A few years later，feeling as if she were put in prison，she abandoned her family．She later married Gottfried Lessing，and they had a son． When Mr．Lessing and her marriage broke up，she and her young son，Peter，moved to London，where she began her writing career．Her first novel，The Grass Is Singing was pfib-lished in Britain in 1 949．Ms Lessing’s strongest influence may be that she inspired a generation of feminists with her breakthrough novel，The Golden Notebook．The book was published in 1962，which wrote about the story of Anna Wulf，a woman who wanted to live freely and Was，in some ways，Ms Lessing’s secondary personality．She wrote about the inner lives of women and rejected the opinion that they should abandon their lives to marriage and children．

Ms Lessing’s family moved from Iran to Zimbabwe because__________．