两道4.12PREP笔记没收的题，技术太差，没能截图

The single family house has constructed by the Yana, a Native American people who lived in what is now Northern California, was conia in shape, its framework of poles laid with slabs of bark, and banked with dirt to a height of 3 to 4 feet.

其中我选了个 dirt as high as 3 to 4 ft. 错的

但原句为什么正确呢？

Technology has allowed manufacturers to make small cars more fuel- effecient than those at any time in their production history.

I choose the original sentence,

but the correct one puts: small cars that are more effecient than those in

还请NN再指点，我要说 他们被允许生产的汽车比那时候多 怎么说？