To a worker, ________ from the point of view of society is necessary labor is from his own point of view voluntary play.
A
本题要求填入一个关系代词引导主语从句，并在主语从句中作主语，所以选what。
There are many sales this season, during which stores will lower their _______ prices.
You’d better leave things ________ if you don ’t know how to deal with them
Sofarscientistshaveonlyacquired________understandingofthephysicalprocessesthatcauseearthquakes.