单项选择题 The old man is in（）habit of going for（）walk along（）river every morning except that it rains.

单项选择题 According to cognitive theories of emotion,()anger occurs when()individuals believe that they have been harmed and that()harm was both avoidable and undeserved．

单项选择题 If laid out in______straight line,______human digestive tract would measure approximately thirty-foot long.