What clause should always be separated from the rest of the sentence by commas

Then she heard his step on the stair away down on the first flight, and she turned white for just a moment. the phrase "she turned white for just a moment" is mainly used to show that della has very fair skin. is afraid of jim's reaction. is beginning to get an illness. had become extremely angry.

Based on the map, which arabian city will marco polo describe after kalhat if he continues northwest across the arabian sea?

The greatest gift the sumerians gave the world was the invention of writing. the sumerians were a wealthy people. they needed some way to keep track of what they owned. they began drawing pictures. they used a reed as a pen. they drew on soft pieces of clay. the soft clay was then dried in the sun. the tablet became a permanent record. later, the sumerian drawings changed into wedge-shaped symbols. this kind of writing is called cuneiform. by putting symbols together, the sumerians could write entire sentences.