Ex.21. Insert prepositions or adverbs where necessary (between, of, for, around, until, before, into, about). Read and translate the following text

For an infant, the mouth is a sensitive portal connecting the world.... him to his developing mind and body. He uses his mouth to meet his mother, to sate his constant hunger, to comfort himself... feedings, and to explore objects in the widening world around him. When hard teeth begin protruding... this soft, sensitive orifice, it is a major event in the life... an infant.

Many parents worry... the timing of the appearance of their children's teeth. While the average time... the appearance of the first teeth is between five and seven months of age, there is a wide normal variation of timing. The teeth might come in as early as one month of age, or they might wait... a child is almost one-and-a-half-years old. Anywhere in this range can be normal.

Generally lower teeth come in... upper teeth, and generally girls' teeth erupt earlier than those of boys. Delayed eruption of all teeth may be the result of a nutritional problem or a systemic condition.