题目

房室瓣能保证心脏内的血液按一定的方向流动，其中血流方向正确的是A．左心室→右心房B．左心房→左心室C．右心室→右心房D．右心室→左心房 答案：B解析:略— What _____ you usually have for breakfast? — _____ and a cup of coffee. A. do, Three breadB. do, Three pieces of bread C. are, Three breads D. are, Three piece of bread