元认知的实质是人对认知活动的自我意识和（ ）。

(单选题)21.（ ） (单选题)Everyone had a form in his hand, but no one knew which offic (单选题)At the conference, people of the different ______ were given (单选题)In their hearts, some American women think it is men’s busin (单选题)As can be seen, the central government is sparing no pains t (单选题)These books were very dear to him and he bought them at ____ (单选题)Which of the following underlined is different in pronunciat (单选题)______ of the land in that area ______ covered with trees an (单选题)—Sir, could you please put out your cigarette. This is a smo (单选题)—How dangerous it was!—Yes, but for the passer-by’s quick ac