that for most of the year they would be unable to cross it. 它们一年中大部分时间都无法穿越这里
To get there, they have to cross the Sonoran desert. 要想到达那里 它们必须穿越索诺兰沙漠
they must cross the Himalayas. 它们必须跨越喜马拉雅山脉