题目内容

设？i表示各类货物运量在总运量中的比例，Li表示各类货物平均运程，Ci表示各类货物在各平均运程区段每吨运费，表示货物平均运价率，则粗略计算货物平均运价率的公式为（）。

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39 Women are good at taking care of children because
A they devote much of their time and attention to them.
B they want to stay at home.
C they were born with this ability.
D they learned to do it at school.

15 There should be laws that prohibit smoking around children.
A advocate B forbid C inherit D withdraw

下面的短文有l5处空白，请根据短文内容为每处空白确定1个最佳选项。
Breastfeeding Can Cut Cardiovascular（心血管的）Risk Breastfeeding can reduce the risk of a heart attack or stroke later in lire and could prevent hundreds of （51）of deaths each year, researchers said on Friday.
Babies who are breastfed have fewer childhood infections and allergies（过敏）and are less
（52）to obesity（肥胖）. British scientists have now shown that breastfeeding and slow
growth in the first weeks and months of life has a protective effect （53） cardiovascular
disease.
“Diets that promote more rapid growth put babies at risk many years later In （54）of raising their blood pressure, raising their cholesterol（胆固醇）and increasing their tendency to diabetes（糖尿病）and obesity—he （55）main risk factors for stroke and heart attack. ”said Professor Alan Lucas of the Institute of Child Health in London.
"Our evidence suggests that the reason why breast-fed babies do better is because they grow more （56） in the early weeks."
Lucas said the effects of breastfeeding on blood pressure and cholesterol later in lire are greater than （57） adults can do to control the risk factors for cardiovascular disease, other than taking drugs.
An estimated l 7 million people die of （58） disease, particularly heart attack and strokes each year, according to the World Health Organization.
Lucas and his colleagues compared the health of 21 6 teenagers （59） as babies had either been breastfed or given different nutritional baby formulas. They reported their （60） in the lancet medical journal.
The teenagers who had been （61） had an l 4-percent lower ratio of bad to good cholesterol and lower concentrations of a protein that is a marker for cardiovascular disease risk.
The researchers also found that （62） of the child's weight at birth, the faster the Infants grew in the early weeks and months of life, the （63）was their later risk of heart disease and stroke. The effect was the （64） for both boys and girls.
"The more human milk you have in the newborn period, the lower your cholesterol level is the lower your blood pressure is l6 years （65）," Lucas said.
51 A hundreds B thousands C millions D numbers

运输需求的交叉弹性系数的计算方法是（）。