Mona Lisa, the mysterious woman in Leonardo da Vinci's 16th century masterpiece, had just given birth to her second son when she sat for the painting, a French art expert said on Tuesday. The discovery was made by a team of Canadian scientists who used special infrared(红外线) and three-dimensional（三维的）technology to study the paint layers on the work, which now sits in the Louvre museum in Paris. Bruno Mottin of the French Museums' Center for Research and Restoration said that on very close examination of the painting it became clear that the Mona Lisa's dress was covered in a thin transparent gauze veil.（透明面纱） 'This type of gauze dress was typical of the kind worn in early 16th century Italy by women who were pregnant or who had just given birth. This is something that had never been seen up to now because the painting was always judged to be dark and difficult to examine,' he told a news conference. 'We can now say that this painting by Leonardo da Vinci was painted in memory of  the birth of the second son of Mona Lisa, which helps us to date it more precisely to around 1503.'The young woman with the ambiguous half smile has been identified as Lisa Gherardini, wife of Florentine merchant Francesco de Giocondo. She had five children. 'People always wrote that Mona Lisa had allowed her hair to hang freely over her shoulders. This greatly surprised historians because letting your hair hang freely during the Renaissance was typical of young girls and women of poor virtue (美德),' he said. The team had hoped to discover more details about Leonardo’s painting techniques, which the artist used to create a hazy (朦胧的) effect. But scientist John Taylor said the team had been disappointed by the lack of brush stroke（笔触）detail on the painting. 小题1:According to the latest research, Mona Lisa was __________. A．a woman of poor virtue B．da Vinci’s second wife C．a woman who was pregnant D．the wife of Florentine merchant 小题2:We can infer from the test that ___________. A．The research has been carried out in France B．Mona Lisa was painted in 1503 at the latest C．In da Vinci’s time women could only wear short hair D．the most difficulty is to identify the paint layers 小题3:What is probably the best title for the test? A．Mona Lisa ,the Mysterious Woman B．Mona Lisa was a New Mother C．Great Discovery in Painting D．Leonardo’s Painting Technique 小题4:The information reported in the text was first got from _______________. A．a newspaper B．the Internet C．a news conference D．the museum