根据我国的国情，今后农业发展主要依靠
Welcome to Wenzhou Zoo! There are many different kinds of animals in the zoo．They come from different countries and they eat different food.
Beibei is a cute panda．She is five years old from China. She is black and white．She likes eating bamboo and drinking water．
Martin is a big elephant．He is ten years old with a long nose．He likes eating grass. People can teach* him to do much work to help them．
Dudu is a monkey. He is two years old from Japan．He likes eating bananas and cakes．He often lives in the trees．
Nick is a lion. He is strong．He is nine years old from England．He likes eating meat. He is very happy in the zoo．
青青草原上，灰太狼每天都想着如何抓羊，而且是屡败屡试，永不言弃．（如图所示）一天，灰太狼在自家城堡顶部A处测得懒羊羊所在地B处的俯角为60°，然后下到城堡的C处，测得B处的俯角为30°．已知AC=50米，若灰太狼以5m/s的速度从城堡底部D处出发，懒羊羊以3m/s沿DB延长线方向逃跑，灰太狼几秒钟后能抓到懒羊羊？
