小弟初学英语有几个疑问,希望高手解答!跪谢~

小弟初学英语有几个疑问,希望高手解答!跪谢~
1.We lost our way in the desert, and ____made matters was that we ran out of water
A.it B that C which D what
求分析,我选的是A但错了,答案是D 求分析原因（若有心人则帮忙说说what 用法）
2.In the Middle Ages people believed it was the earth ,not the sun , ____the center of our planetary system
A.was that B that was C was D that
此题说的是考查强调句,可是为什么that 前可以放逗号?你也许会说这不是定语从句,但我觉得是啊.求分析?
还有一个问题就是为什么选B 而不选AD 我选的是A求高手分析原因