题目

阅读理解    North American black bears are shy animals．They are fearful by nature，and will usually run away if they see or hear people．Because of this，it can be difficult for scientists to learn about these animals．    In order to study black bears, researchers from New Jersey，USA，catch bears and use drugs to help them go to sleep．Researchers then work out the size and the weight of the bear, take blood to test for diseases，remove a tooth and take it to the lab to find out its age．From these studies。researchers want to find out how many bears live in New J78÷2=120÷4=90+90÷3=19×3=80÷16=（100-50）÷50=250÷2=360÷12=2×25+25×0=