The writer of the article was, no doubt ______.

单项选择题It is true that ______.

单项选择题The author's main purpose in the passage is to ______.

单项选择题In discussing Landes's work, the author's tone is ______.

单项选择题This school (para. 5) refers to people who ______.

单项选择题According to Landes, the main reason that some countries are so poor is that ______.