单项选择题
A．a sure sign of a psychological problem in a child B．something hardly to be expected in a young child C．an inevitable phase of children's mental development D．a mental scale present in all humans, including children
A．through contact with society B．gradually and under guidance C．naturally and by biological instinct D．through exposure to social information
A．He feels amused by their premature behavior. B．He thinks it is a phenomenon worthy of note. C．He considers it a positive development. D．He seems to be upset about it.