在△ABC中，AB=4，AC=3，AD是△ABC的角平分线，则△ABD与△ACD的面积之比是​____ .

被称为“遗传学之父”的科学家是（ ）

    Computers are popular (受欢迎的) now. 1 can do many things on the computer. It is 2 for us to learn to use it. But some children 3 much time on computer games. That's 4 

    I have got a computer at home and I 5 it  with my parents. I often do my homework on it and when I'm 6 I listen to music on it. My 7 usually use the computer at weekends. What do they do 8 the computer? My father sees movies. My mother does 9 things. She does some shopping and talks with my grandparents on the Internet.

    Have you got 10  computer in your home?

货币产生前是物物交换,公式是商品—商品;货币产生后是商品流通,公式是商品—货币—商品。物物交换和商品流通的不同点是（  ）

①前者不属于商品交换,后者属于商品交换　②前者没有交换的媒介,后者有交换的媒介　③前者交换是为了得到使用价值,后者是为了得到价值　④前者买卖同时进行,后者包括先卖后买两个阶段