Who is the president of Singapore?

Explanation:

The current president of Singapore is Halimah Yacob. Halimah Yacob has been serving as president since 2017.

(d) rivers.

explanation:

civilizations developed around rivers because their waters provided places to hunt and fish. also, as the rivers flooded, the lands around them became fertile. this allowed them to support farming. this is especially true of the nile river, which flooded the same time each year.

the difference is that white collar worker performs skills like worker as a scientist or well blue collars do physical work and they do services like being a cook.