Which two are true about has-a and is-a relationships？（） [" Inheritance represents an is-a relationship."," Inheritance represents a has-a relationship."," Interfaces must be used when creating a has-a relationship."," Instance variables can be used when creating a has-a relationship."]
根据动机的归因理论，在能力高低、努力程度和身心状态三种因素中，属于可控的内在因素是（） ["能力高低","努力程度","身心状态","以上均不是"]
论述UASB与IC优缺点对比。
你认为这本书是有价值的，而别人却认这为它毫无用处，原因在于（） ["缺乏沟通","相互之间有矛盾","过分自信","个体价值观的差异"]
长期存放在库内的钢材，如使庠内的相对湿度比库外低（），就能起到很好的缓蚀作用。 ["5%-10%","10%-15%","15%-20%","20%-300%"]
简述英国学前教育机构的主要举办机构和类型
