He has come to be recognized as an expert in the problem of overpopulation and food supply.
由于他的经验促使他终于成为了公认的人口过剩和食物供应问题的专家。
For him, caves have the same peculiar fascination which high mountains have for the climber.
对洞穴探险者来说,洞穴有一种特殊的魅力,就像高山对登山者有特殊魅力一样。