单项选择题The love story of Margaret and Thornton in the novel North and South implicates Gaskell’s view on marriage that the couple’s experiencing ups and downs together is an essential part of a happy and long-lasting marriage. ( )
多项选择题蚕丝中的丝素由18种氨基酸组成，其中含量最多的是哪三种氨基酸。（）A、甘氨酸B、丙氨酸C、亮氨酸D、丝氨酸
