多项选择题
A.presentPopoverFromBarButtonItem：permittedArrowDirections：animated：呈现Popover视图方法 B.dismissPopoverAnimated：关闭Popover视图方法 C.popoverVisible，判断Popover视图是否可见 D.popoverArrowDirection，判断Popover视图箭头的方向
A.ABAddressBook B.ABPerson C.ABGroup D.ABRecord
A.OCUnit B.GHUnit C.OCMock D.NSXML