题目

Everyone knows the smart black-and-white dog that sits on top of a red doghouse with his best friend---a bird called Woodstock. Created by the American cartoonist Charles Schulz in 1950, the clever dog is loved by generations of kids and adults. He speaks more than 20 languages and appears daily in 26,000 newspapers around the world. When Snoopy first appeared, he was not different form other pet dogs. But two years later, he had begun to speak with simple words and sounds. By 1957 he could walk on two legs and was going to school with his master, Charlie Brown, who failed in just about everyt下列物质通过细胞膜是需要载体的是           A．水分子进入根毛细胞B．氧进入肺泡细胞C．钾离子被小肠绒毛上皮细胞吸收D．二氧化碳进入毛细血管