题目

下列各种遗传病中属于染色体病的是（ ） A．原发性高血压B．抗维生素D佝偻病C．21三体综合征D．白化病 答案：C ---Learning a language isn’t easy．It takes time． ---I agree．________．There is no short cut． A．All roads lead to Rome                             Rome was not built in a day C．Practice makes perfect                             D．Slow but sure wins the race