根据短文内容，选择正确答案。

D

    Astronauts (宇航员) face many problems when living in space stations. One of them is food. People on Earth put together all the meals first and then send these meals to space stations by space shuttle. Because the food has to last a long time (sometimes up to three months), people have to store a lot of it in cans. The space station does not have a fridge, but it has a cool room to keep fruit and vegetables fresh. Astronauts also eat many other foods such as dried meat that do not need special care.

    Without the help of gravity sitting down to eat can be difficult. Astronauts sometimes have to fix themselves to the wall while eating. They also have to be very careful so that food does not float away.

合理的制度是实现社会公平的重要力量。下列制度一定程度上促进了社会公平的是（   ）

一项考古统计表明，我国新石器时代稻谷遗存120余处，其中长江流域90余处，黄河流域12处，另有闽、浙、台数处。炭化粟粒、粟壳遗存40余处，分布于山东、河北、浙江、新疆等省区。据此可以推断(  )

①我国已由采集进入种植的时代        ②我国的原始农业南北各具特色

③南北之间粮食品种已有交流         ④我国北方种植粮食早于南方