宋代地主利用农民之间的矛盾，用增租转佃方式试图增加地租，而农民则利用地主之间的矛盾，用转佃他人之田的方式来达到降低地租的目的。在这一斗争过程中，地租剥削率自然维持在一个合理的水平上。材料意在强调宋代（    ）

宇宙中有一些由二颗或多颗星球组成的天体系统，它们离其他星系很远，与其他星系相互作用的万有引力可忽略不计，依靠彼此的万有引力而运动，关于这些星系，下列说法正确的是（   ）

苏伊士运河沟通了（　　）

    Little Tom likes cartoons very much .When the cartoons begin on TV, he does nothing until they' re over. Sometimes he'd rather wait for a long time and go to bed late. In the morning his mother has to wake him up, or he will be late for school.
    Yesterday Tom heard there would be an interesting cartoon today. This morning, as soon as he got up, he turned the television, but didn't receive the programme. He had to have breakfast and then went to school. After school he ran home while his mother was cooking supper in the kitchen (厨房). He hurried to the sitting room and turned on the television again, but he couldn’t find the cartoon. He rushed into the kitchen and asked his mother to help.
    “It's only five now,”said the woman. “Your programme will be after supper.”
    “Well, let's have supper right now!”