分子式为C_NH_2NO₂的羧酸和某醇酯化生成分子式为C_N+2H_2N+4O₂的酯，反应所需羧酸和醇的质量比为1∶1，则该羧酸是

A．乙酸

B．丙酸

C．甲酸

D．乙二酸

The first and most important agents of socialization are the people who care for infants. In the earliest months, messages from nurturers constitute the child’’s basic understanding of the world around it. This is the infant’’s first introduction to the language that shapes perception and elicits emotion.Another powerful source of information and socialization is the friendship of peers. Peers are equals that one can deal with on the same level as oneself, whereas parents are superiors. The heavy emotional overlay of family relationships makes some kinds of learning difficult.Much formal socialization is placed in the hands of professionals. Teachers from kindergarten on are specifically designated agents of socialization. Ideally, a teacher is one who has both knowledge and the skills to present it. During the course of teaching their subjects, classroom instructors provide role models and attempt to convey the excitement of learning itself.In earlier times, parents, friends and teachers would comprise the list of primary childhood socializers. Children’’s books, comics and magazines might also have been mentioned as sources of information on norms and role models. Today one must add three powerful indirect or non-personal socialization agents: radio, movies and television. Many people learn about politics, form a vision of well-being, and develop attitudes towards others from what they see on the screen and hear through the speakers.

Peers are one of the ________agents of socialization.

A．formal

B．indirect

C．primary

D．personal