产力包括哪3种？各有何特点？
参考答案：
产力的来源及其特点如下：
（1）子宫收缩力：是临产后主要产力，能迫使宫颈缩短，子宫颈口扩张，胎先露下降及胎盘娩出。正常宫缩具有节律性、对称性、极性及缩复作用。
（2）腹肌及膈肌收缩力：是第二产程时娩出胎儿的重要辅助力量，在第三产程还可促使胎盘娩出，此种产力在第二产程末配合宫缩运用最为有效。
（3）肛提肌收缩力：有协助胎先露部在骨盆腔内旋转的作用，还能协助胎头仰伸娩出。当胎儿娩出后，胎盘降至 * * 时，肛提肌收缩有助于胎盘娩出。
Complete the following passage by using the words in the box. Each word can only be used once. Note that there is one word more than you need.
they buy in cinemas, according to the Food Standard Agency. Smaller popcorn buckets and drink cups should also be made 1 , the nutrition inspector said. Tim Smith, chief executive of the agency, told The Times that cinemas should help to deal with the country's overweight 2 . "There is a misbelief that popcorn is calorie-free, but that is not the case. It is a 3 to us," he said. "Portion sizes are also a big issue, and there seems to be increasingly big packs on sale." He spoke as a number of food chains such as Pret A Manger, Wimpey and The Real Greek 4 to put calorie counts on all their menus. A trial scheme(试行方案) with 21 food companies took place last summer, and 5 are that consumers altered their buying habits when they realised the number of calories in a product. A consultation(征询意见) on the trial ends next month but Mr Smith is already planning the second drive for American-style calorie counts and is 6 to win support from cinemas and other entertainment places, from football grounds to concert halls. Government 7 suggest that two thirds of adults and a third of children are overweight. If trends are not 8 , this could rise to almost nine in ten adults and two thirds of children by 2050, putting them at 9 risk of heart disease, cancer and other diseases. |