What were the three major occupational divisions within the medieval society?

Suppose you need to verify how correctly use commas you open ur english textbook and scan the chaper titles in which one would most likey find the information you need

Arrange the sentences below to form a logical paragraph. an experienced rock climber knows that it takes a combination of knowledge and preparation to perform a successful climb. a successful climb begins with a proper foothold, carefully placing each foot on a ledge or crack then reaching for a solid hold, and finally pushing off. in addition to a proper foothold, a climber must be careful to check the integrity of the rock before stepping because it has to be solid clear through. a veteran climber judges the integrity of the rock and chooses not to climb on conglomerates, packed clay with lots of little rocks. but, such knowledge of rock is not the only preparation a skilled climber needs; equally important is the correct equipment. with these tools, knowledge of rock composition and equipment safety, a climber may experience many safe and enjoyable climbs.

Which resource is most useful for finding the correct spelling of words?