To explain this, they hypothesise that galaxies must contain a great deal of missing matter which cannot be detected. 为了解释这一点，他们假定各星系一定包含了大量无法探测到的不明物质。
Villagers say the fence would restrict public access to the hills.村民们说这个围栏将限制公众进入山区。The villagers piped in drinking water from the reservoir.村民用管道从水库引来饮用水。Soon the villagers couldn't afford to buy food for themselve...