方位介词in/on/behind/in front of — 英语填空题
题目
在学校教室里，黑板在墙上，讲台在黑板前面，椅子在讲台后面，课本放在书包里。用 in、on、behind 或 in front of 填空：The blackboard is ___ the wall. The teacher’s desk is ___ the blackboard. The chair is ___ the desk. The book is ___ the schoolbag.